Condensed Consolidated Statement 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	$ 99,505	$ 112,992	$ 261,023	$ 281,879
Derivative financial instruments:
Unrealized holding gains/(losses)	(452)	(2,870)	(5,214)	87
Gains/(losses) reclassified to net income	351	(216)	3,032	(483)
Total other comprehensive income (loss)	(101)	(3,086)	(2,182)	(396)
Comprehensive income	$ 99,404	$ 109,906	$ 258,841	$ 281,483