Income Taxes - Reconciliation of Income Tax Expense At US Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense computed at U.S. Federal statutory income tax rate	$ 30,972	$ 29,437	$ 35,217
State income taxes	7,543	3,674	2,714
Permanent items	1,332	(2,196)	(2,311)
Research and development credits	(2,071)	(3,199)	(2,196)
Uncertain income tax position	(2,992)	716	(1,137)
Effect of rate changes	0	0	9,694
Other	(353)	751	1,353
Income tax expense	$ 34,431	$ 29,183	$ 43,334