Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal									$ 4,981	$ 174	$ 0
State and local									567	2	(49)
Current Income Tax Expense (Benefit), Total									5,548	176	(49)
Deferred:
Federal									949	2,460	(767)
State and local									131	308	(90)
Deferred Income Tax Expense (Benefit)									1,080	2,768	(857)
Expense (benefit) for income taxes	$ (1,071)	$ 2,933	$ 2,962	$ 1,804	$ (603)	$ 663	$ 1,714	$ 1,170	$ 6,628	$ 2,944	$ (906)