Mergers and Acquisitions - ActoGeniX - Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2015
Business Acquisition [Line Items]
Goodwill	$ 153,289	$ 157,175	$ 165,169
ActoGeniX NV
Business Acquisition [Line Items]
Cash				$ 3,180
Other receivables				305
Prepaid expenses and other				31
Property, plant, and equipment				209
Intangible assets				68,100
Other noncurrent assets				23
Total assets acquired				71,848
Accounts payable				230
Accrued compensation and benefits				196
Other accrued liabilities				253
Deferred revenue				732
Deferred tax liabilities				612
Total liabilities assumed				2,023
Net assets acquired				69,825
Goodwill				2,649
Total consideration				$ 72,474