Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Sep. 30, 2011
Consolidated Balance Sheets [Abstract]
Interest-earning deposits	$ 148,323	$ 105,292
Available-for-sale Securities, Amortized Cost	1,528,191	1,443,529
Held-to-maturity securities, fair value	2,193,944	2,434,392
Loans receivable, allowance for loan losses	$ 15,605	$ 15,465
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	167,498,133	167,498,133
Common stock, shares outstanding	167,498,133	167,498,133