Income Taxes - Statutory Rate and Provisions for Income Taxes Percent (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory tax rate	21.00%	35.00%	35.00%
State income taxes, net of federal benefit	5.70%	4.40%	3.80%
Nondeductible expenses	2.60%	3.20%	2.60%
Uncertain tax position	(1.30%)		(3.30%)
TCJA Enactment	0.00%	(22.90%)	0.00%
Excess Tax Benefit	(2.60%)	(1.60%)	0.00%
Credits and other	0.70%	(0.10%)	(0.40%)
Effective tax rate	26.10%	18.00%	37.70%