CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 43,004	$ 39,050	$ 119,825	$ 117,818
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) on available-for-sale investment securities	(965)	(35,001)	(4,409)	(21,378)
Reclassification adjustment of net gain (loss) from sale of available-for-sale securities included in net income	0	9,639	0	9,639
Related tax benefit (expense)	355	9,320	1,620	4,314
Other comprehensive income (loss) for available for sale securities, net of tax	(610)	(16,042)	(2,789)	(7,425)
Net unrealized gain (loss) on long-term borrowing hedge	(10,290)	5,587	(20,978)	(3,646)
Related tax benefit (expense)	3,782	(2,053)	7,709	1,340
Other comprehensive income (loss) on long term borrowing hedge, net of tax	(6,508)	3,534	(13,269)	(2,306)
Other comprehensive income (loss) net of tax	(7,118)	(12,508)	(16,058)	(9,731)
Comprehensive income	$ 35,886	$ 26,542	$ 103,767	$ 108,087