Investment in Change Healthcare Joint Venture (Details) - USD ($)			3 Months Ended		12 Months Ended
	Mar. 09, 2020	Jul. 01, 2019	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 10, 2020	Apr. 01, 2019	Mar. 31, 2018	Mar. 31, 2017
Schedule of Equity Method Investments [Line Items]
Shares distributed in split-off (shares)	176,000,000.0
Common stock, par value (in dollars per share)			$ 0.01		$ 0.01	$ 0.01
Net gain from sale of equity method investment, pre-tax					$ 0	$ 0	$ 56,000,000
Cumulative effect adjustment			$ 5,309,000,000		175,000,000	5,309,000,000	8,287,000,000			$ 10,057,000,000
Equity earnings and charges from investment in Change Healthcare Joint Venture					$ (48,000,000)	(36,000,000)	(43,000,000)
Opening retained earnings adjustments: adoption of new accounting standard
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment			(13,000,000)			(13,000,000)	11,000,000			154,000,000
Tax Receivable Agreement (“TRA”)
Schedule of Equity Method Investments [Line Items]
Percentage of net cash tax savings realized or deemed realized under TRA (percent)					85.00%
Due from Related Parties			0		$ 0	0
Separation of Change Healthcare JV
Schedule of Equity Method Investments [Line Items]
Shares distributed in split-off (shares)	176,000,000.0
Shares of common stock exchanged (shares)	15,400,000
Number of shares converted into per share converted (shares)								1
Common stock, par value (in dollars per share)								$ 0.001
Retained Earnings
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment			13,022,000,000		8,202,000,000	13,022,000,000	12,409,000,000			12,986,000,000
Retained Earnings | Opening retained earnings adjustments: adoption of new accounting standard
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment			(13,000,000)			(13,000,000)	11,000,000		$ 69,000,000	$ 154,000,000
Prescription Technology Solutions | Tax Receivable Agreement (“TRA”) | Change Healthcare
Schedule of Equity Method Investments [Line Items]
Pre-tax credit representing reduction in TRA liability							90,000,000
Noncurrent liability			0		$ 0	0
Change Healthcare
Schedule of Equity Method Investments [Line Items]
Net gain from sale of equity method investment, pre-tax	$ 414,000,000
Change Healthcare, Inc.
Schedule of Equity Method Investments [Line Items]
Net cash proceeds from IPO		$ 888,000,000
Proceeds from other security offering		$ 279,000,000
Change Healthcare, Inc. | IPO
Schedule of Equity Method Investments [Line Items]
Offering price (in usd per share)		$ 13
Change Healthcare, Inc. | Change Healthcare
Schedule of Equity Method Investments [Line Items]
Ownership interest in Joint Venture (percent)		41.50%
Contributions made in exchange for additional membership interests		$ 609,000,000
Corporate Joint Venture
Schedule of Equity Method Investments [Line Items]
Ownership interest in Joint Venture (percent)											70.00%
Pre-tax dilution loss				$ 246,000,000
Corporate Joint Venture | Transition Services Agreements (“TSA”)
Schedule of Equity Method Investments [Line Items]
Total fees charged under the TSA						22,000,000	60,000,000
Corporate Joint Venture | Change Healthcare
Schedule of Equity Method Investments [Line Items]
Ownership interest in Joint Venture (percent)		58.50%
Pre-tax dilution loss						246,000,000
Pre-tax other-than-temporary impairment				$ 1,200,000,000		1,200,000,000
Net gain from sale of equity method investment, pre-tax			$ 414,000,000
Equity earnings and charges from investment in Change Healthcare Joint Venture						$ 119,000,000	194,000,000
Pre-tax credit representing reduction in TRA liability							$ (90,000,000)
Corporate Joint Venture | Change Healthcare | ASU 2014-09 | Retained Earnings | Opening retained earnings adjustments: adoption of new accounting standard
Schedule of Equity Method Investments [Line Items]
Cumulative effect adjustment									$ 80,000,000
Corporate Joint Venture | Change Healthcare, Inc.
Schedule of Equity Method Investments [Line Items]
Ownership interest in Joint Venture (percent)											30.00%