Fair Value - Other Fair Value Disclosures (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, net of current maturities	$ 7,315,000,000		$ 7,315,000,000		$ 5,470,000,000
Goodwill impairment	53,000,000	$ 0	2,940,000,000	$ 0
Tangible asset impairment charges	0	0	0	0
Impairment of intangible assets	0	0	0	0
Impairment of other intangible assets	0	$ 0	0	$ 0
Fair value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, net of current maturities	7,100,000,000		7,100,000,000		5,600,000,000
Carrying value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, net of current maturities	$ 7,000,000,000.0		$ 7,000,000,000.0		$ 5,600,000,000