CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 40,236	$ 35,282
Other comprehensive income (loss) net of tax:
Net unrealized gain (loss) on available-for-sale securities	(9,661)	(2,636)
Related tax benefit (expense)	3,478	969
Other comprehensive loss	(6,183)	(1,667)
Comprehensive income	$ 34,053	$ 33,615