Debt (Schedule of Debt Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2014 2015 Convertible Senior Notes	Sep. 30, 2013 2015 Convertible Senior Notes	Mar. 31, 2010 2015 Convertible Senior Notes	Jun. 30, 2014 2018 Convertible Senior Notes	Sep. 30, 2013 2018 Convertible Senior Notes	Jun. 30, 2013 2018 Convertible Senior Notes
Debt Instrument [Line Items]
Principal	$ 776,250	$ 776,250	$ 287,500	$ 287,500	$ 287,500	$ 488,750	$ 488,750	$ 488,800
Unamortized Discount	(93,326)	(116,558)	(10,513)	(19,898)		(82,813)	(96,660)
Notes Issuance Costs	(9,912)	(12,459)	(1,119)	(2,176)		(8,793)	(10,283)
Carrying Value	$ 673,012	$ 647,233	$ 275,868	$ 265,426		$ 397,144	$ 381,807