Investment Securities - Contractual Maturities of Investment Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Due in one year, Amortized Cost	$ 720
Due after one year through five years, Amortized Cost	44,295
Due after five years through ten years, Amortized Cost	120,195
Due after ten years, Amortized Cost	182,650
Total investment securities available for sale, Amortized Cost	986,105
Due in one year, Fair Value	724
Due after one year through five years, Fair Value	43,520
Due after five years through ten years, Fair Value	117,815
Due after ten years, Fair Value	175,428
Total investment securities available for sale, Fair Value	958,656
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities without a single maturity date, Amortized Cost	590,225
Securities without a single maturity date, Fair Value	573,827
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities without a single maturity date, Amortized Cost	48,020
Securities without a single maturity date, Fair Value	$ 47,342