Securities - Schedule of Contractual Maturity of Securities Available for Sale, Excluding Equity Securities (Detail) $ in Thousands	Sep. 30, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
1 year or less, Amortized Cost	$ 25,281
1 year - 5 years, Amortized Cost	190,387
5 years - 10 years, Amortized Cost	94,600
After 10 years, Amortized Cost	30,132
Total, Amortized Cost	340,400
1 year or less, Fair Value	25,501
1 year - 5 years, Fair Value	195,612
5 years - 10 years, Fair Value	95,971
After 10 years, Fair Value	30,550
Total, Fair Value	347,634
Total debt securities, Amortized Cost	578,858
Total debt securities, Fair Value	586,340
Residential and Multi-Family Mortgage [Member]
Schedule of Available-for-sale Securities [Line Items]
Mortgage & asset backed securities, Amortized Cost	184,471
Mortgage & asset backed securities, Fair Value	184,347
Pooled SBA [Member]
Schedule of Available-for-sale Securities [Line Items]
Mortgage & asset backed securities, Amortized Cost	53,987
Mortgage & asset backed securities, Fair Value	$ 54,359