Securities - Additional Information (Detail) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Investments Debt And Equity Securities [Abstract]
Available-for-sale securities transferred to held-to-maturity securities		$ 536,000,000
Unrealized net loss on securities transferred from held-to-maturity to available -for-sale, Gross				13,347,000
Net Realized gains on the sale of securities	348,000		42,000	348,000	42,000
Corporate debt securities, callable, amortized cost	55,000,000			55,000,000
Corporate debt securities, callable, estimated fair value	$ 47,100,000			$ 47,100,000
Floating-rate securities, purchased period				1998
Floating-rate debt securities, fixed interest rate period				Over 90-day LIBOR
Principal maturity year				2028 or prior if called by the issuer