Selected Quarterly Financial Data (Summary Of Quarterly Data) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Selected Quarterly Financial Information [Abstract]
Total interest and dividend income	$ 74,234	$ 71,921	$ 71,857	$ 72,234	$ 72,223	$ 73,675	$ 74,980	$ 77,676	$ 290,246	$ 298,554	$ 328,051
Net interest and dividend income	47,973	46,198	45,727	44,245	43,806	44,404	44,320	45,630	184,143	178,160	184,881
Provision for credit losses	427	307	160	515	(500)	(800)	0	233	1,409	(1,067)	2,040
Net income	$ 20,210	$ 19,983	$ 19,688	$ 17,813	$ 16,067	$ 17,995	$ 17,715	$ 17,563	$ 77,694	$ 69,340	$ 74,513
Basic EPS	$ 0.15	$ 0.14	$ 0.14	$ 0.12	$ 0.11	$ 0.13	$ 0.12	$ 0.12	$ 0.56	$ 0.48	$ 0.47
Diluted EPS	$ 0.15	$ 0.14	$ 0.14	$ 0.12	$ 0.11	$ 0.13	$ 0.12	$ 0.12	$ 0.56	$ 0.48	$ 0.47
Dividends declared per share	$ 0.075	$ 0.325	$ 0.075	$ 0.505	$ 0.075	$ 0.075	$ 0.075	$ 0.775	$ 0.98	$ 1.00	$ 0.40
Average number of basic shares outstanding	137,047,000	138,332,000	139,489,000	142,882,000	142,856,000	143,263,000	145,382,000	147,883,000	139,440,073	144,847,156	157,912,978
Average number of diluted shares outstanding	137,051,000	138,334,000	139,489,000	142,883,000	142,858,000	143,263,000	145,382,000	147,883,000	139,441,964	144,848,009	157,916,400