Investment Securities - Contractual Maturities of Investment Securities Available for Sale (Detail) $ in Thousands	Jun. 30, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Due in one year, Amortized Cost	$ 10,750
Due after one year through five years, Amortized Cost	91,209
Due after five years through ten years, Amortized Cost	123,271
Due after ten years, Amortized Cost	64,416
Total investment securities available for sale, Amortized Cost	1,183,648
Due in one year, Fair Value	10,749
Due after one year through five years, Fair Value	92,467
Due after five years through ten years, Fair Value	124,178
Due after ten years, Fair Value	63,290
Total investment securities available for sale, Fair Value	1,186,341
Residential mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Securities without a single maturity date, Amortized Cost	873,480
Securities without a single maturity date, Fair Value	876,153
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Securities without a single maturity date, Amortized Cost	20,522
Securities without a single maturity date, Fair Value	$ 19,504