Income Taxes - Components of Consolidated Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 16,407	$ 22,477	$ 35,602
State	1,004	732	1,603
Total Current	17,411	23,209	37,205
Deferred:
Federal	(1,389)	12,965	(2,120)
State	(73)	(165)	(129)
Total Deferred	(1,462)	12,800	(2,249)
Income tax expense, Total	$ 15,949	$ 36,009	$ 34,956