Income Taxes - Summary of Income Tax Expense (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current expense (benefit):
Federal									$ 25,176	$ 7,978	$ 25,156
State									12,904	(493)	(5,549)
Total current expense									38,080	7,485	19,607
Deferred expense:
Federal									10,658	(7,539)	(13,888)
State									16,496	23,992	25,343
Total deferred expense									27,154	16,453	11,455
Income tax expense	$ 18,336	$ 17,049	$ 15,460	$ 14,389	$ (10,987)	$ 10,179	$ 12,474	$ 12,272	$ 65,234	$ 23,938	$ 31,062