Securities - Debt Securities Available for Sale by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Amortized Cost And Fair Value Debt Securities [Abstract]
Due in one year or less, amortized cost
Due after one year through five years, amortized cost
Due after five years through ten years, amortized cost	186,149
Due after ten years through fifteen years, amortized cost	61,447
Mortgage-backed GSE securities: residential, amortized cost	297,517
Total amortized cost	545,113
Due in one year or less,
Due after one year through five years, fair value
Due after five years through ten years, fair value	174,498
Due after ten years through fifteen years, fair value	56,218
Mortgage-backed GSE securities: residential, fair value	286,214
Total fair value	$ 516,930