Income Taxes - Provision for Income Taxes Applicable to Income Before 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
Current:
Federal									$ 22,540	$ 20,707	$ 24,634
State									3,977	3,542	2,061
Deferred:
Tax reform remeasurement											12,765
Federal									7,736	6,864	13,329
State									88	299	1,018
Total	$ 7,046	$ 8,334	$ 10,103	$ 8,858	$ 10,556	$ 6,516	$ 7,335	$ 7,004	$ 34,341	$ 31,412	$ 53,807