Reconciliation of Differences from U.S. Federal Statutory Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Expenses [Line Items]
Pretax book income	$ 163,311	$ 98,462	$ 77,623
Federal tax expense at 35% statutory rate	57,159	34,462	27,168
State and local income taxes	6,190	4,808	3,870
Benefit of domestic production deduction	(5,255)	(2,010)	0
Other	928	272	56
Total income tax expense	$ 59,022	$ 37,532	$ 31,094