Healthcare Technology Net Asset Exchange (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Mar. 01, 2017
Schedule of Equity Method Investments [Line Items]
Payments received on Healthcare Technology Net Asset Exchange					$ 126	$ 0
Net losses from Change Healthcare	$ 61			$ 0	181	$ 0
Carrying value of investment	3,795		$ 4,063		3,795
Tax Receivable Agreement (“TRA”) | Change Healthcare, LLC (“Change Healthcare”)
Schedule of Equity Method Investments [Line Items]
Noncurrent liability	136		136		136
Joint Venture | Transition Services Agreements (“TSA”)
Schedule of Equity Method Investments [Line Items]
Reimbursements for transition services fees	10				47
Receivables from joint venture	58				58
Change Healthcare, LLC (“Change Healthcare”)
Schedule of Equity Method Investments [Line Items]
Net Loss					(9)
Change Healthcare, LLC (“Change Healthcare”) | Core MTS Businesses | Operating Segments | Technology Solutions
Schedule of Equity Method Investments [Line Items]
Gain on Healthcare Technology Net Asset Exchange		$ 37	3,947
Gain from sale of business, after tax		$ 22	$ 3,018
Payments received on Healthcare Technology Net Asset Exchange	$ 126
Change Healthcare, LLC (“Change Healthcare”) | Joint Venture
Schedule of Equity Method Investments [Line Items]
Net Loss					$ (13)
Expected ownership interest in the joint venture (percent)	70.00%				70.00%		70.00%
Net losses from Change Healthcare	$ 61				$ 181
Carrying value of investment	3,795				3,795
Excess of carrying value of investment over proportional share of book value	$ 4,671				$ 4,671