Income Taxes - Current and Deferred 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:
Federal									$ 22,427	$ 41,578	$ 4,163
State									10,354	2,493	1,731
Total current									32,781	44,071	5,894
Deferred:
Federal									1,650	(17,302)	39,003
State									24	(1,239)	1,631
Total deferred									1,674	(18,541)	40,634
Income tax expense (benefit)	$ 8,026	$ 9,938	$ 8,802	$ 7,689	$ 6,026	$ 8,575	$ 4,568	$ 6,361	$ 34,455	$ 25,530	$ 46,528