Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 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 available-for-sale to held-to-maturity, Gross	(13,347,000)
Realized gains or losses on the sale of securities	0		0
Corporate debt securities, callable, amortized cost	55,000,000
Corporate debt securities, callable, estimated market value	$ 45,000,000
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