Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Composition of Financial Instruments (Detail)

v2.4.1.9
Financial Instruments - Composition of Financial Instruments (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 60,512us-gaap_AvailableForSaleSecuritiesAmortizedCost $ 60,555us-gaap_AvailableForSaleSecuritiesAmortizedCost
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 14us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax 8us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments (21)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax (50)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Fair Value 60,505us-gaap_AvailableForSaleSecurities 60,513us-gaap_AvailableForSaleSecurities
Cash and cash equivalents [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost (2,000)us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember 		(1,858)us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember 		0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember 		0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember
Fair Value (2,000)us-gaap_AvailableForSaleSecurities
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember 		(1,858)us-gaap_AvailableForSaleSecurities
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_CashAndCashEquivalentsMember
Investments [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 58,512us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember 		58,697us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 14us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember 		8us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments (21)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember 		(50)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember
Fair Value 58,505us-gaap_AvailableForSaleSecurities
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember 		58,655us-gaap_AvailableForSaleSecurities
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_InvestmentsMember
US Government Agencies Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 25,116us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember 		27,154us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 8us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember 		5us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments (5)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember 		(8)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Fair Value 25,119us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember 		27,151us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Corporate Debt Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 33,396us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember 		31,543us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 6us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember 		3us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments (16)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember 		(42)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value 33,386us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember 		31,504us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Money market funds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 2,000us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember 		1,858us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember
Available-for-sale Securities Gross Unrealized Gain Accumulated in Investments 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember 		0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember
Available-for-sale Securities Gross Unrealized Loss Accumulated in Investments 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember 		0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember
Fair Value $ 2,000us-gaap_AvailableForSaleSecurities
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember 		$ 1,858us-gaap_AvailableForSaleSecurities
/ us-gaap_InvestmentTypeAxis
= us-gaap_MoneyMarketFundsMember