Investments (Unrealized Losses) (Details) (USD $) In Thousands	Sep. 30, 2011	Sep. 30, 2010
Schedule of Investments [Line Items]
Investment securities available for sale, less than 12 months, fair value	$ 1,076,407
Investment securities available for sale, 12 months or more, fair value	2,100
Investment securities available for sale, total fair value	1,078,507
Investment securities available for sale, less than 12 months, unrealized losses	2,583
Investment securities available for sale, 12 months or more, unrealized losses	50
Investment securities available for sale, total unrealized losses	2,633
Government Agency Securities [Member]
Schedule of Investments [Line Items]
Investment securities available for sale, less than 12 months, fair value	1,051,017
Investment securities available for sale, 12 months or more, fair value	0
Investment securities available for sale, total fair value	1,051,017
Investment securities available for sale, less than 12 months, unrealized losses	2,435
Investment securities available for sale, 12 months or more, unrealized losses	0
Investment securities available for sale, total unrealized losses	2,435
Residential Mortgage-Backed Securities [Member]
Schedule of Investments [Line Items]
Investment securities available for sale, less than 12 months, fair value	25,390	10,364
Investment securities available for sale, 12 months or more, fair value	1,675	535
Investment securities available for sale, total fair value	27,065	10,899
Investment securities available for sale, less than 12 months, unrealized losses	148	88
Investment securities available for sale, 12 months or more, unrealized losses	50	22
Investment securities available for sale, total unrealized losses	198	110
Investment securities held to maturity, less than 12 months, fair value	0	0
Investment securities held to maturity, 12 months or more, fair value	22	27
Investment securities held to maturity, total fair value	22	27
Investment securities held to maturity, less than 12 months, unrealized losses	0	0
Investment securities held to maturity, 12 months or more, unrealized losses	26	26
Investment securities held to maturity, total unrealized losses	26	26
State, County, Municipal [Member]
Schedule of Investments [Line Items]
Investment securities available for sale, less than 12 months, fair value	0
Investment securities available for sale, 12 months or more, fair value	425
Investment securities available for sale, total fair value	425
Investment securities available for sale, less than 12 months, unrealized losses	0
Investment securities available for sale, 12 months or more, unrealized losses	0
Investment securities available for sale, total unrealized losses	$ 0

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