Income Taxes - Statutory Rate and Provisions for Income Taxes Percent (Detail)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal Statutory Tax Rate		35.00%	35.00%	35.00%
State Income Taxes, net of federal benefit		4.40%	3.80%	3.90%
Nondeductible Expense		3.20%	2.60%	2.50%
Uncertain tax position		(0.00%)	(3.30%)
TCJA Enactment	(22.90%)	(22.90%)	(0.00%)	(0.00%)
Excess Tax Benefit		(1.60%)	(0.00%)	(0.00%)
Credits and other		(0.10%)	(0.40%)	0.00%
Effective Tax Rate		18.00%	37.70%	41.40%