Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Sep. 30, 2013
Consolidated Balance Sheets [Abstract]
Interest-earning deposits	$ 94,431	$ 99,735
Available-for-sale Securities, Amortized Cost	887,543	1,058,283
Held-to-maturity securities, estimated fair value	1,735,084	1,741,846
Loans receivable, allowance for credit losses	$ 8,967	$ 8,822
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	143,120,893	147,840,268
Common stock, shares outstanding	143,120,893	147,840,268