Income Taxes - Difference Between Customary Rate and Effective Tax Rate on Income Before Income Taxes Due (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at statutory rate	35.00%	35.00%	35.00%
Tax effect of:
Effect of the Tax Cuts and Jobs Act net of valuation allowance	14.80%
Valuation allowance on deferred tax assets	(31.80%)	(54.60%)	(23.50%)
State taxes, net of federal tax benefit	0.70%	14.70%	1.40%
Nondeductible compensation	(1.10%)	(0.10%)
Net operating loss expirations	(1.20%)
Other	(2.50%)	(0.60%)
Effective tax rate	13.90%	(5.60%)	12.90%