Consolidated Statements Of Stockholders' Equity - 3 months ended Dec. 31, 2016 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Unearned Compensation ESOP [Member]	Retained Earnings [Member]	AOCI [Member]
Balance at Sep. 30, 2016	$ 1,392,964	$ 1,375	$ 1,156,855	$ (39,647)	$ 268,466	$ 5,915
Net income	20,578				20,578
Other comprehensive income (loss), net of tax	(1,314)					(1,314)
ESOP activity, net	634		222	412
Restricted stock activity, net	14		14
Stock-based compensation	157		157
Stock options exercised	5,340	4	5,336
Cash dividends to stockholders ($0.38 per share)	(50,198)				(50,198)
Balance at Dec. 31, 2016	$ 1,368,175	$ 1,379	$ 1,162,584	$ (39,235)	$ 238,846	$ 4,601