| Commitments and Contingencies Sublease Income, Leased Facilities (Details) - USD ($) $ in Millions | 12 Months Ended | |
|---|---|---|
| Dec. 31, 2018 | Dec. 31, 2017 | |
| Commitments and Contingencies Disclosure [Abstract] | ||
| Operating Leases, Income Statement, Sublease Revenue | $ 2.4 | $ 2.1 | 
| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition The amount of revenue recognized for the period under subleasing arrangements. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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