Income Taxes - Reconciliation of Provision (Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax at statutory rate	$ 28,150	$ 24,432	$ 23,675
State taxes, net of federal benefit	3,548	2,010	2,717
Effect of U.S. tax reform (the Tax Act)	13,074	0	0
Effect of net income (loss) attributable to noncontrolling interests	(1,017)	(91)	1,492
Change in valuation allowance	(2,613)	(5,125)	7,812
Other, net	(652)	(182)	1,276
Income tax expense (benefit)	$ 40,490	$ 21,044	$ 36,972
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax at statutory rate	35.00%	35.00%	35.00%
State taxes, net of federal benefit	4.00%	3.00%	4.00%
Effect of U.S. tax reform (the Tax Act)	16.00%	0.00%	0.00%
Effect of net income (loss) attributable to noncontrolling interests	(1.00%)	(0.00%)	2.00%
Change in valuation allowance	(3.00%)	(7.00%)	12.00%
Other, net	(1.00%)	(1.00%)	2.00%
Income tax expense (benefit)	50.00%	30.00%	55.00%