Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Goodwill
Beginning balance		$ 3,332,816	$ 3,247,105	$ 3,332,816
Goodwill acquired			8,785	65,129
Goodwill, Purchase Accounting Adjustments			(58)	(1,283)
Goodwill, Transfers				0
Effect of foreign currency translation			(12,368)	(7,776)
Ending balance	$ 3,247,105		3,243,464	3,247,105
Goodwill, Impairment Loss				(141,781)
Mobile Reporting Unit [Member]
Goodwill
Beginning balance		1,241,010	0	1,241,010
Goodwill acquired				0
Goodwill, Purchase Accounting Adjustments				2,697
Goodwill, Transfers				(1,249,051)
Effect of foreign currency translation				5,344
Ending balance	0	36,000		0
Goodwill, Impairment Loss	(400)	(35,100)		0
Healthcare
Goodwill
Beginning balance		1,418,334	1,430,325	1,418,334
Goodwill acquired			8,785	14,936
Goodwill, Purchase Accounting Adjustments			113	(705)
Goodwill, Transfers				0
Effect of foreign currency translation			(4,079)	(2,240)
Ending balance	1,430,325		1,435,144	1,430,325
Goodwill, Impairment Loss				0
Mobile and Consumer
Goodwill
Goodwill acquired			0
Goodwill, Purchase Accounting Adjustments			0
Effect of foreign currency translation			0
Ending balance			0
Automotive
Goodwill
Beginning balance		0	1,119,947	0
Goodwill acquired			0	50,193
Goodwill, Purchase Accounting Adjustments			(171)	(3,275)
Goodwill, Transfers				1,080,453
Effect of foreign currency translation			(4,208)	(7,424)
Ending balance	1,119,947	1,080,500	1,115,568	1,119,947
Goodwill, Impairment Loss				0
Enterprise
Goodwill
Beginning balance		673,472	683,347	673,472
Goodwill acquired			0	0
Goodwill, Purchase Accounting Adjustments			0	0
Goodwill, Transfers				11,991
Effect of foreign currency translation			(3,444)	(2,116)
Ending balance	683,347		679,903	683,347
Goodwill, Impairment Loss				0
Other Segments [Member]
Goodwill
Beginning balance		$ 0	13,486	0
Goodwill acquired			0	0
Goodwill, Purchase Accounting Adjustments			0	0
Goodwill, Transfers				156,607
Effect of foreign currency translation			(637)	(1,340)
Ending balance	$ 13,486		$ 12,849	13,486
Goodwill, Impairment Loss				$ 141,781

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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