Segment and Geographic Information and Significant Customers - Segment Profit to Income Before Income Taxes (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2017
Segment Reporting Information [Line Items]
Total segment revenues	[1]									$ 1,829,387		$ 1,856,479		$ 1,759,642
Revenues		$ 470,658	$ 449,197	$ 409,583	$ 493,654	$ 479,432	$ 449,449	$ 466,193	$ 447,224	1,823,092	[1]	1,842,298	[1]	1,728,175	[1]
Segment profit										612,922		604,260		551,172
Corporate expenses and other, net										(139,806)		(195,704)		(121,935)
Acquisition-related revenues and costs of revenue adjustment										(6,295)		(14,181)		(31,467)
Non-cash stock based compensation										(141,212)		(142,909)		(142,901)
Amortization of intangible assets										(103,563)		(124,883)		(150,731)
Acquisition-related costs, net										(8,909)		(16,093)		(27,708)
Restructuring and other charges, net										(80,465)		(57,026)		(59,923)
Goodwill and Intangible Asset Impairment										0		(170,941)		0
Other income (expense), net										(106,928)		(129,747)		(171,177)
Income (loss) before income taxes										25,744		(247,224)		(154,670)
Healthcare
Segment Reporting Information [Line Items]
Total segment revenues	[1]									950,593		984,819		899,341
Revenues										949,730
Segment profit										337,471		326,658		257,825
Enterprise
Segment Reporting Information [Line Items]
Total segment revenues	[1]									510,753		483,194		474,317
Revenues										510,078
Segment profit										141,479		140,478		133,913
Automotive
Segment Reporting Information [Line Items]
Total segment revenues	[1]									306,580		279,402		252,218
Revenues										301,821
Segment profit										110,559		109,111		118,248
Other Segments [Member]
Segment Reporting Information [Line Items]
Total segment revenues	[1]									61,461		109,064		133,766
Segment profit										23,413		28,013		41,186
Series of Individually Immaterial Business Acquisitions [Member]
Segment Reporting Information [Line Items]
Revenues	[1]									$ (6,295)		$ (14,181)		$ (31,467)

[1] Segment revenues differ from reported revenues due to certain revenue adjustments related to acquisitions that would otherwise have been recognized but for the purchase accounting treatment of the business combinations. These revenues are included to allow for more complete comparisons to the financial results of historical operations and in evaluating management performance.