| Income Taxes Income Tax (Tables)
 | 12 Months Ended | 
| Dec. 31, 2018 | 
|---|
| Income Tax Disclosure [Abstract] |  | 
| Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] | 
The domestic and international components of income (loss) before income taxes are presented as follows:
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Years Ended December 31, |  
|   | 2018 |   | 2017 |   | 2016 |  
|   | (in thousands) |  
| Domestic | $ | 16,405 | 
 |   | $ | 42,580 | 
 |   | $ | 75,778 | 
 |  
| Foreign | (49,257 | ) |   | (76,578 | ) |   | (12,088 | ) |  
| Income (loss) before income taxes | $ | (32,852 | ) |   | $ | (33,998 | ) |   | $ | 63,690 | 
 |  | 
| Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] | 
The income tax provision (benefit) consists of the following:
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Years Ended December 31, |  
|   | 2018 |   | 2017 |   | 2016 |  
|   | (in thousands) |  
| Current: |   |   |   |   |   |  
| Federal | $ | 3,292 | 
 |   | $ | 13,470 | 
 |   | $ | 1,216 | 
 |  
| State | 37 | 
 |   | 26 | 
 |   | (11 | ) |  
| Foreign | 1,640 | 
 |   | 1,784 | 
 |   | 1,092 | 
 |  
| Total current | 4,969 | 
 |   | 15,280 | 
 |   | 2,297 | 
 |  
| Deferred: |   |   |   |   |   |  
| Federal | 788 | 
 |   | 19,451 | 
 |   | 17,492 | 
 |  
| State | (2,799 | ) |   | (4,668 | ) |   | (8,271 | ) |  
| Foreign | (3,884 | ) |   | (3,697 | ) |   | (2,459 | ) |  
| Change in valuation allowance | (5,727 | ) |   | (51,177 | ) |   | (6,661 | ) |  
| Total deferred | (11,622 | ) |   | (40,091 | ) |   | 101 | 
 |  
| Total income tax provision (benefit) | $ | (6,653 | ) |   | $ | (24,811 | ) |   | $ | 2,398 | 
 |  | 
| Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] | 
The actual income tax provision (benefit) differs from the amount computed using the federal statutory rate as follows:
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Years Ended December 31, |  
|   | 2018 |   | 2017 |   | 2016 |  
|   | (in thousands) |  
| Provision (benefit) at statutory rate | $ | (6,814 | ) |   | $ | (11,899 | ) |   | $ | 22,294 | 
 |  
| State income taxes (net of federal benefit) | 20 | 
 |   | 17 | 
 |   | (13 | ) |  
| Research and development credits | (8,849 | ) |   | (8,153 | ) |   | (9,076 | ) |  
| Foreign rate differential | 8,640 | 
 |   | 23,666 | 
 |   | 2,888 | 
 |  
| Stock compensation | 74 | 
 |   | (5,713 | ) |   | (5,756 | ) |  
| Foreign deemed dividend | 1,103 | 
 |   | — | 
 |   | 51 | 
 |  
| Transaction costs | — | 
 |   | 553 | 
 |   | 749 | 
 |  
| Provision to return | (27 | ) |   | (917 | ) |   | — | 
 |  
| Uncertain tax positions | 1,463 | 
 |   | 1,993 | 
 |   | (1,204 | ) |  
| Foreign tax credits | — | 
 |   | (5 | ) |   | (72 | ) |  
| Permanent and other | 1,319 | 
 |   | 1,730 | 
 |   | (802 | ) |  
| Foreign unremitted earnings | 1,960 | 
 |   | (1,368 | ) |   | — | 
 |  
| Tax Act | 185 | 
 |   | 25,205 | 
 |   | — | 
 |  
| Other tax rate changes | — | 
 |   | 1,257 | 
 |   | — | 
 |  
| Valuation allowance | (5,727 | ) |   | (51,177 | ) |   | (6,661 | ) |  
| Total income tax provision (benefit) | $ | (6,653 | ) |   | $ | (24,811 | ) |   | $ | 2,398 | 
 |  | 
| Schedule of Deferred Tax Assets and Liabilities [Table Text Block] | 
The components of the deferred income tax assets are as follows:
|  |  
|  |  |  |  |  |  |  |  |  
|   | December 31, |  
|   | 2018 |   | 2017 |  
|   | (in thousands) |  
| Deferred tax assets: |   |   |   |  
| Net operating loss carryforwards | $ | 64,887 | 
 |   | $ | 77,355 | 
 |  
| Research and development credits | 75,032 | 
 |   | 69,668 | 
 |  
| Accrued expenses and other | 7,965 | 
 |   | 10,506 | 
 |  
| Accrued compensation | 2,504 | 
 |   | 2,444 | 
 |  
| Stock-based compensation | 2,550 | 
 |   | 2,659 | 
 |  
| Intangible assets | — | 
 |   | — | 
 |  
|   | 152,938 | 
 |   | 162,632 | 
 |  
| Less valuation allowance | (79,196 | ) |   | (84,560 | ) |  
|   | 73,742 | 
 |   | 78,072 | 
 |  
| Deferred tax liabilities: |   |   |   |  
| Fixed assets | (1,391 | ) |   | (1,777 | ) |  
| Intangible assets | (20,833 | ) |   | (35,981 | ) |  
| Unremitted foreign earnings | — | 
 |   | (436 | ) |  
| Net deferred tax assets | $ | 51,518 | 
 |   | $ | 39,878 | 
 |  | 
| Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block] | 
The following table summarizes the changes to the unrecognized tax benefits during 2018, 2017 and 2016:
|  |  
|  |  |  |  |  
|   | (in thousands) |  
| Balance as of December 31, 2015 | $ | 26,053 | 
 |  
| Additions based on tax positions related to the current year | 2,025 | 
 |  
| Decreases based on tax positions of prior year | (4,661 | ) |  
| Balance as of December 31, 2016 | $ | 23,417 | 
 |  
| Additions based on tax positions related to the current year | 3,037 | 
 |  
| Additions related to acquisitions | 37,090 | 
 |  
| Decreases based on tax positions of prior year | (458 | ) |  
| Balance as of December 31, 2017 | $ | 63,086 | 
 |  
| Additions based on tax positions related to the current year | 3,080 | 
 |  
| Decreases based on tax positions of prior year | (4,696 | ) |  
| Balance as of December 31, 2018 | $ | 61,470 | 
 |  |