Commitments and Contingencies - Summary of Unfunded Commitments (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Unfunded credit extension commitments	$ 1,070,092	$ 951,741
Commitments to fund loans
Line of Credit Facility [Line Items]
Unfunded credit extension commitments	686,149	578,730
Unused lines of credit
Line of Credit Facility [Line Items]
Unfunded credit extension commitments	361,925	358,601
Commercial and standby letters of credit
Line of Credit Facility [Line Items]
Unfunded credit extension commitments	$ 22,018	$ 14,410