Income Taxes - Summary of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets:
Net operating loss carryforwards	$ 23,030	$ 25,745
Tax credits	52,902	43,838
Compensation	18,791	15,934
Deferred revenue	25,599	27,587
Research and development expense deferral	0	12,631
Other	4,065	5,393
Gross deferred income tax assets	124,387	131,128
Less: valuation allowance	(7,653)	(20,415)
Net deferred income tax assets	116,734	110,713
Deferred income tax liabilities:
Depreciation and amortization	(52,978)	(60,872)
Deferred revenue	(44,198)	(54,508)
Total deferred income tax liabilities	(97,176)	(115,380)
Net deferred income taxes, deferred income tax asset	19,558
Net deferred income taxes, deferred income tax liability		(4,667)
Deferred income taxes / liabilities included in the balance sheet are:
Deferred income tax asset – noncurrent	51,611	27,048
Deferred income tax liability – noncurrent	(32,053)	(31,715)
Net deferred income taxes, deferred income tax asset	$ 19,558
Net deferred income taxes, deferred income tax liability		$ (4,667)