CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 37,910	$ 37,338	$ 116,803	$ 108,598
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) on available-for-sale securities	22,026	(10,697)	28,527	(12,925)
Related tax benefit (expense)	(8,095)	3,931	(10,484)	4,750
Other comprehensive income (loss)	13,931	(6,766)	18,043	(8,175)
Comprehensive income	$ 51,841	$ 30,572	$ 134,846	$ 100,423