Securities - Debt Securities Available for Sale by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
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	500
Due after five years through ten years, amortized cost	161,153
Due after ten years through fifteen years, amortized cost	88,615
Mortgage-related securities, amortized cost	322,394
Total amortized cost	572,662
Due in one year or less, fair value
Due after one year through five years, fair value	501
Due after five years through ten years, fair value	149,827
Due after ten years through fifteen years, fair value	79,435
Mortgage-related securities, fair value	312,652
Total fair value	$ 542,415