Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2015	Sep. 30, 2014	Mar. 31, 2014
Financial assets that are measured at fair value on a recurring basis
Marketable equity securities			$ 2,727
Holding period adjustment	$ 132
Contingent consideration	(2,914)	$ (3,758)	(3,594)
Net financial assets (liabilities)	5,781	(2,606)	754
Foreign currency forward [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	8,563	1,152	1,621
Convertible notes hedges [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	27,215	36,994
Convertible notes embedded derivative [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative liability	(27,215)	(36,994)
Level 1 [Member]
Financial assets that are measured at fair value on a recurring basis
Marketable equity securities			2,727
Holding period adjustment	0
Contingent consideration	0	0	0
Net financial assets (liabilities)	0	0	2,727
Level 1 [Member] | Foreign currency forward [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0	0
Level 1 [Member] | Convertible notes hedges [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0
Level 1 [Member] | Convertible notes embedded derivative [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative liability	0	0
Level 2 [Member]
Financial assets that are measured at fair value on a recurring basis
Marketable equity securities			0
Holding period adjustment	132
Contingent consideration	0	0	0
Net financial assets (liabilities)	8,695	1,152	1,621
Level 2 [Member] | Foreign currency forward [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	8,563	1,152	1,621
Level 2 [Member] | Convertible notes hedges [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	27,215	36,994
Level 2 [Member] | Convertible notes embedded derivative [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative liability	(27,215)	(36,994)
Level 3 [Member]
Financial assets that are measured at fair value on a recurring basis
Marketable equity securities			0
Holding period adjustment	0
Contingent consideration	(2,914)	(3,758)	(3,594)
Net financial assets (liabilities)	(2,914)	(3,758)	(3,594)
Level 3 [Member] | Foreign currency forward [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0	$ 0
Level 3 [Member] | Convertible notes hedges [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0
Level 3 [Member] | Convertible notes embedded derivative [Member]
Financial assets that are measured at fair value on a recurring basis
Derivative liability	$ 0	$ 0