Commitments and Contingent Liabilities - Reserve for Unfunded Loan Commitments and for Repurchase of Previously Sold Loans (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Reserve for unfunded commitment losses beginning balance	$ 2,848	$ 5,444	$ 2,557	$ 4,664
Provision for unfunded commitments	258	(2,401)	549	(1,621)
Ending reserve for unfunded commitment losses	3,106	3,043	3,106	3,043
Reserve for repurchased loans beginning balance	865	2,351	1,338	2,600
Charge off	0	(233)	(164)	(233)
Recovery	10	0	74	0
Provision for repurchased loans	(1)	136	(374)	(113)
Ending reserve for repurchased loans	$ 874	$ 2,254	$ 874	$ 2,254