Accumulated stock holders' Deficit - Change in AOCL (Details) $ in Thousands	9 Months Ended
	Jun. 30, 2018 USD ($)
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, Beginning Balance	$ (363,616)
Accumulated other comprehensive loss, Ending Balance	(326,209)
Interest rate caps
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, Beginning Balance	(1,084)
Other comprehensive (loss) income before reclassification, net of tax	1,815
Accumulated other comprehensive loss, Ending Balance	731
Foreign currency translation adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, Beginning Balance	(80,752)
Other comprehensive (loss) income before reclassification, net of tax	(11,986)
Accumulated other comprehensive loss, Ending Balance	(92,738)
AOCI attributable to parent
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive loss, Beginning Balance	(81,836)
Other comprehensive (loss) income before reclassification, net of tax	(10,171)
Accumulated other comprehensive loss, Ending Balance	$ (92,007)