Income Taxes - Effective Tax Rate Reconciliation (Details)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Income Tax Disclosure [Abstract]
U.S. federal statutory tax rate (percent)	21.00%	21.00%
State income taxes, net of federal tax benefit	1.30%	1.50%
General business credits	(2.60%)	(2.00%)
Employee stock-based compensation	(0.70%)	(3.70%)
IRC 162(m) limitation	4.50%	1.90%
Nondeductible expenses	0.40%	0.20%
Other	(0.50%)	0.20%
Effective tax rate (percent)	23.40%	19.10%