Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2016	Sep. 30, 2015	Jun. 30, 2015
Financial assets that are measured at fair value on a recurring basis
Holding Period Adjustment		$ 4	$ 47
Phantom share-based awards		(3,932)
Contingent consideration		(2,601)	(2,836)
Net financial assets	$ 7,044	7,640	8,484
Foreign currency forwards
Financial assets that are measured at fair value on a recurring basis
Derivative assets	7,044	14,169	11,273
Cash Convertible Notes Hedges
Financial assets that are measured at fair value on a recurring basis
Derivative assets	16,200	10,505	23,160
Cash Convertible Notes Embedded Derivative
Financial assets that are measured at fair value on a recurring basis
Derivative liability	(16,200)	(10,505)	(23,160)
Level 1
Financial assets that are measured at fair value on a recurring basis
Holding Period Adjustment		0	0
Phantom share-based awards		0
Contingent consideration		0	0
Net financial assets	0	0	0
Level 1 | Foreign currency forwards
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0	0
Level 1 | Cash Convertible Notes Hedges
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0	0
Level 1 | Cash Convertible Notes Embedded Derivative
Financial assets that are measured at fair value on a recurring basis
Derivative liability	0	0	0
Level 2
Financial assets that are measured at fair value on a recurring basis
Holding Period Adjustment		4	47
Phantom share-based awards		0
Contingent consideration		0	0
Net financial assets	7,044	14,173	11,320
Level 2 | Foreign currency forwards
Financial assets that are measured at fair value on a recurring basis
Derivative assets	7,044	14,169	11,273
Level 2 | Cash Convertible Notes Hedges
Financial assets that are measured at fair value on a recurring basis
Derivative assets	16,200	10,505	23,160
Level 2 | Cash Convertible Notes Embedded Derivative
Financial assets that are measured at fair value on a recurring basis
Derivative liability	(16,200)	(10,505)	(23,160)
Level 3
Financial assets that are measured at fair value on a recurring basis
Holding Period Adjustment		0	0
Phantom share-based awards		(3,932)
Contingent consideration	(1,500)	(2,601)	(2,836)
Net financial assets	0	(6,533)	(2,836)
Level 3 | Foreign currency forwards
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0	0
Level 3 | Cash Convertible Notes Hedges
Financial assets that are measured at fair value on a recurring basis
Derivative assets	0	0	0
Level 3 | Cash Convertible Notes Embedded Derivative
Financial assets that are measured at fair value on a recurring basis
Derivative liability	$ 0	$ 0	$ 0