Income Taxes - Provision for Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal income taxes currently payable									$ 22,908	$ 12,256
State income taxes currently payable									4,490	4,601
Federal income taxes deferred									20,402	(1,513)	$ 31,915
Revaluation of deferred tax assets											39,300
State income taxes deferred									4,350	2,506	1,724
Deferred income tax expense									24,752	993	72,939
Income tax expense	$ 11,433	$ 13,254	$ 14,359	$ 13,104	$ 3,223	$ 5,325	$ 4,345	$ 4,957	$ 52,150	$ 17,850	$ 72,939