Income Taxes - Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
Federal net operating loss	$ 101,662	$ 79,356
State net operating loss	59,126	46,571
Foreign net operating loss	34,407	35,710
Research and development expense	2,893	4,038
Tax credits	21,669	20,040
Stock options	30,430	28,830
Accruals	6,294	5,719
Equity investments	12,904	8,454
Bad debts	414	20,302
Lease liability	1,370	2,205
Foreign credits	10,837	11,113
Equity securities	2,447	2,406
Other	11,668	17,448
Deferred income tax assets	296,121	282,192
Deferred income tax liabilities:
Intangible assets	(250,640)	(280,962)
Fixed assets	(3,486)	(5,572)
Other	(2,272)	(2,325)
Deferred income tax liabilities	(256,398)	(288,859)
Net deferred income tax assets (liabilities)	39,723	(6,667)
Valuation allowance	(154,916)	(142,062)
Net deferred income tax liabilities	$ (115,193)	$ (148,729)