Income Taxes (Details 4) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Components of net deferred tax assets (liabilities)
Depreciation and amortization	$ 13,199	$ 13,995
Lease liabilities	8,716	10,734
Other timing differences, accruals and reserves	5,347	9,522
Deferred equity compensation	4,631	4,456
Net operating loss carryovers	15,756	20,900
Tax credits	169,063	233,407
Total gross deferred tax assets	216,712	293,014
Lease right-of-use assets	(6,392)	(10,400)
Convertible debt	(130)	(151)
Deferred revenue	(45,845)	(94,763)
Total gross deferred tax liabilities	(52,367)	(105,314)
Total net deferred tax assets before valuation allowance	164,345	187,700
Valuation allowance	(174,328)	(196,972)
Net deferred tax liabilities	$ (9,983)	$ (9,272)