Income Taxes - Summary of Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current expense:
Federal									$ 51,147	$ 8,483	$ 25,176
State									28,898	5,500	12,904
Total current expense									80,045	13,983	38,080
Deferred (benefit) expense:
Federal									(17,463)	49,169	10,658
State									5,683	27,679	16,496
Total deferred expense									(11,780)	76,848	27,154
Income tax expense	$ 18,074	$ 18,046	$ 18,961	$ 13,184	$ 34,958	$ 17,088	$ 20,714	$ 18,071	$ 68,265	$ 90,831	$ 65,234