Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012
Consolidated Balance Sheets [Abstract]
Interest-earning deposits	$ 69,236	$ 127,544
Available-for-sale Securities, Amortized Cost	1,226,591	1,367,925
Held-to-maturity securities, fair value	1,974,115	1,969,899
Loans receivable, allowance for credit losses	$ 10,477	$ 11,100
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,400,000,000	1,400,000,000
Common stock, shares issued	152,115,857	155,379,739
Common stock, shares outstanding	152,115,857	155,379,739