Income Taxes - Schedule of Components of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income taxes:
Federal taxes									$ 26,164	$ 36,005	$ 23,857
State and local taxes									6,513	4,342	3,847
Deferred income taxes:
Federal taxes									3,455	17,899	5,135
State and local taxes									(77)	0	235
Total	$ 8,486	$ 9,893	$ 6,907	$ 10,769	$ 27,864	$ 10,942	$ 10,850	$ 8,590	$ 36,055	$ 58,246	$ 33,074