Income Taxes - Components 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
Federal									$ 1,991	$ 18,030	$ (12,754)
State									740	108	169
Total current									2,731	18,138	(12,585)
Deferred
Federal									18,846	(4,568)	35,440
State									(2,793)	0	0
Total deferred									16,053	(4,568)	35,440
Income tax expense (benefit)	$ 3,181	$ 6,302	$ 4,465	$ 4,836	$ 4,269	$ 5,278	$ 3,018	$ 1,005	$ 18,784	$ 13,570	$ 22,855