Income Taxes Expense - 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, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax expense computed at U.S. federal statutory income tax rate	$ 35,417	$ 30,972	$ 29,437
State income taxes	7,281	7,543	3,674
Permanent items	2,654	1,332	(2,196)
Research and development credits	(3,602)	(2,071)	(3,199)
Uncertain income tax position	348	(2,992)	716
Other	(400)	(353)	751
Income tax expense	$ 41,698	$ 34,431	$ 29,183