Investment in Change Healthcare Joint Venture (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jul. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Apr. 01, 2019	Mar. 31, 2019	Apr. 01, 2018	Mar. 31, 2017
Schedule of Equity Method Investments [Line Items]
Cumulative-effect adjustment to beginning retained earnings						$ 11,000,000		$ 154,000,000
Net income (loss) from Change Healthcare		$ (1,454,000,000)	$ (56,000,000)	$ (1,450,000,000)	$ (112,000,000)
Carrying value of investment		2,167,000,000		2,167,000,000			$ 3,513,000,000
Transition Services Agreements (“TSA”)
Schedule of Equity Method Investments [Line Items]
Fees incurred or earned from TSA			26,000,000		36,000,000
Noncurrent liability			90,000,000		90,000,000
Change Healthcare JV | Tax Receivable Agreement (“TRA”)
Schedule of Equity Method Investments [Line Items]
Noncurrent liability		0		0			0
Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)	58.50%								70.00%
Loss expected to be recognized		246,000,000
Loss expected to be recognized, net of tax		184,000,000
Carrying value of investment		2,167,000,000		2,167,000,000			3,513,000,000
Excess of carrying amount over book value of investment		2,090,000,000		2,090,000,000			$ 4,158,000,000
Pre-tax credit recognized on relief from potential future obligations			90,000,000		90,000,000
After-tax credit recognized on relief from potential future obligations					66,000,000
Change Healthcare JV | Joint Venture
Schedule of Equity Method Investments [Line Items]
Pre-tax impairment charge		1,157,000,000
After-tax impairment charge		864,000,000
Net income (loss) from Change Healthcare		$ (51,000,000)	$ (56,000,000)	$ (47,000,000)	$ (112,000,000)
Retained Earnings
Schedule of Equity Method Investments [Line Items]
Cumulative-effect adjustment to beginning retained earnings						11,000,000		$ 154,000,000
Change Healthcare, Inc.
Schedule of Equity Method Investments [Line Items]
IPO cash proceeds	$ 888,000,000
Proceeds from concurrent offering of other securities	279,000,000
Change Healthcare, Inc. | Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)									30.00%
Change Healthcare, Inc. | Change Healthcare JV
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)		41.50%		41.50%
Contributions made in exchange of additional interest	$ 609,000,000
ASU 2014-09 | Retained Earnings | Change Healthcare JV | Joint Venture
Schedule of Equity Method Investments [Line Items]
Cumulative-effect adjustment to beginning retained earnings						$ 80,000,000
Initial public offering | Change Healthcare, Inc.
Schedule of Equity Method Investments [Line Items]
Offering price	$ 13