Income Taxes - Summary of Effective Tax Rate Differed from U.S. Statutory Federal Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Statutory federal tax rate	21.00%	21.00%	35.00%
State taxes, net of federal benefit	6.20%	0.30%	(4.00%)
Adjustment for final positions on filed returns	(0.20%)	(1.10%)	(1.10%)
Nondeductible expenses and other, net	1.30%	1.20%	1.50%
Federal and state tax credits	(7.50%)	(6.40%)	(7.70%)
Change in federal tax rate			3.20%
Other, net	0.20%		(0.10%)
Total	21.00%	15.00%	26.80%