CONDENSED CONSOLIDATED STATEMENT OF SHAREHOLDERS' EQUITY - 6 months ended Mar. 31, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	COMMON STOCK [Member]	CAPITAL INEXCESS OF PAR VALUE [Member]	RETAINED EARNINGS [Member]	TREASURY SHARES [Member]	ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) [Member]	DEFERRED COMPENSATION [Member]
Balance at Sep. 30, 2017	$ 398,808	$ 20,166	$ 487,077	$ 480,347	$ (489,225)	$ (60,481)	$ (39,076)
Balance (in Shares) at Sep. 30, 2017		80,663			33,557
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	121,269			121,269
Dividend	(49,650)			(49,650)
Shares withheld on employee taxes on vested equity awards			0
Shares withheld on employee taxes on vested equity awards					197
Shares withheld on employee taxes on vested equity awards	(4,446)				$ (4,446)
Amortization of deferred compensation	1,672						1,672
Common stock acquired (in shares)					1,438
Common stock acquired	(28,415)				$ (28,415)
Equity awards granted, net (in shares)		811
Equity awards granted, net	0	$ 203	(203)
ESOP allocation of common stock	1,101		1,101
Stock-based compensation	4,920		4,920
Other comprehensive income, net of tax	28,759					28,759
Balance at Mar. 31, 2018	$ 474,018	$ 20,369	$ 492,895	$ 551,966	$ (522,086)	$ (31,722)	$ (37,404)
Balance (in Shares) at Mar. 31, 2018		81,474			35,192