Income Taxes - Component of Income Tax Expense Benefit (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
Current expense
Federal									$ 7,647	$ 6,399	$ 13,653
State									(503)	(684)	1,093
Deferred expense
Federal									(5,024)	288	(957)
State									(1,933)	(91)	(581)
Deferred tax revaluation expense											5,323
Income tax expense	$ (2,970)	$ 2,117	$ 706	$ 334	$ 122	$ 1,068	$ 2,263	$ 2,459	$ 187	$ 5,912	$ 18,531