Investment Securities - Contractual Maturities of Investment Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Due in one year, Amortized Cost	$ 115
Due after one year through five years, Amortized Cost	74,498
Due after five years through ten years, Amortized Cost	86,184
Due after ten years, Amortized Cost	131,918
Total investment securities available for sale, Amortized Cost	821,322
Due in one year, Fair Value	115
Due after one year through five years, Fair Value	75,570
Due after five years through ten years, Fair Value	81,561
Due after ten years, Fair Value	120,676
Total investment securities available for sale, Fair Value	796,583
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities without a single maturity date, Amortized Cost	506,034
Securities without a single maturity date, Fair Value	495,604
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities without a single maturity date, Amortized Cost	22,573
Securities without a single maturity date, Fair Value	$ 23,057