Income Taxes - Components of Consolidated Income Tax Expense (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 tax expense
Federal									$ 20,403	$ 13,109	$ 17,835
State									12,655	9,323	6,650
Current tax expense, Total									33,058	22,432	24,485
Deferred tax expense
Federal									695	1,842	11,418
State									997	758	1,055
Deferred tax benefit, Total									1,692	2,600	12,473
Total tax expense	$ 8,826	$ 9,386	$ 7,443	$ 9,095	$ 7,334	$ 6,476	$ 5,782	$ 5,440	$ 34,750	$ 25,032	$ 36,958