Income Taxes - Schedule of Income (Loss) Before Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal income tax at statutory rate, amount									$ 30,973	$ 22,185	$ 17,604
Federal income tax at statutory rate, percentage of pretax income									35.00%	35.00%	35.00%
State income tax, amount									$ 1,434	$ 1,355	$ 353
State income tax, percentage of pretax income									1.62%	2.14%	0.70%
Tax-exempt interest, net of disallowance amount									$ (277)	$ (249)	$ (148)
Tax-exempt interest, net of disallowance percentage of pretax income									(0.31%)	(0.39%)	(0.30%)
Bank-owned life insurance, amount									$ (2,422)	$ (1,296)	$ (868)
Bank-owned life insurance, percentage of pretax income									(2.73%)	(2.04%)	(1.73%)
Other, amount									$ 204	$ (1,821)	$ 663
Other, percentage of pretax income									0.22%	(2.88%)	1.33%
Total	$ 7,415	$ 8,415	$ 6,400	$ 7,682	$ 7,289	$ 3,940	$ 5,517	$ 3,429	$ 29,912	$ 20,174	$ 17,604
Effective income tax rate, percentage of pretax income									33.80%	31.83%	35.00%