Goodwill and Intangible Assets Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Document Period End Date	Mar. 31, 2019
Balance as of September 30, 2018	$ 450,001
Acquisitions		$ 2,000
Amortization	(52,735)
Effect of foreign currency translation	(442)
Balance at March 31, 2019	398,312
Other Acquisitions [Member]
Finite-Lived Intangible Assets [Line Items]
Acquisitions	$ 1,488