Income Taxes - Current and Long-Term Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Accrued liabilities	$ 96,292	$ 80,557
Loss and credit carryforwards	14,830	59,502
Assets relating to equity compensation	19,653	24,874
Other assets	14,092	30,236
Gross deferred tax assets	144,867	195,169
Property, equipment, and leasehold improvements	(3,421)	(962)
Intangible assets	(214,580)	(372,542)
Prepaid expenses	(41,926)	(35,126)
Other liabilities	(61,068)	(6,584)
Gross deferred tax liabilities	(320,995)	(415,214)
Valuation allowance	(4,066)	(3,192)
Net deferred tax liabilities	$ (180,194)	$ (223,237)