Debt - Schedule of Debt (Details)	9 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2018 GBP (£)	Dec. 31, 2018 EUR (€)	Mar. 31, 2018 USD ($)
Short-term debt and current maturities of long-term debt
Euro-denominated commercial paper	$ 800,000,000			$ 863,000,000
Current maturities of long-term debt	240,000,000			439,000,000
Current maturities of capitalized lease liabilities	540,000,000			616,000,000
Short-term debt and current maturities of long-term debt	1,580,000,000			1,918,000,000
Long-term debt, net of current maturities
Long-term debt	6,760,000,000			7,147,000,000
Less: current maturities	780,000,000			1,055,000,000
Long-term debt, net of current maturities	5,980,000,000			6,092,000,000
Term loan | GBP term loan
Long-term debt, net of current maturities
Long-term debt	$ 0			260,000,000
Debt Information [Abstract]
Effective interest rate	1.30%	1.30%	1.30%
Term loan | EUR term loan
Long-term debt, net of current maturities
Long-term debt	$ 0			493,000,000
Debt Information [Abstract]
Effective interest rate	1.75%	1.75%	1.75%
Term loan | AUD term loan
Long-term debt, net of current maturities
Long-term debt	$ 563,000,000			0
Debt Information [Abstract]
Effective interest rate	2.72%	2.72%	2.72%
Term loan | AUD term loan
Long-term debt, net of current maturities
Long-term debt	$ 0			210,000,000
Term loan | GBP term loan
Long-term debt, net of current maturities
Long-term debt	$ 571,000,000			0
Debt Information [Abstract]
Effective interest rate	1.60%	1.60%	1.60%
Term loan | EUR term loan
Long-term debt, net of current maturities
Long-term debt	$ 0			187,000,000
Debt Information [Abstract]
Effective interest rate	0.90%	0.90%	0.90%
Term loan | USD term loan
Long-term debt, net of current maturities
Long-term debt	$ 0			899,000,000
Senior notes | Senior notes due 2020
Long-term debt, net of current maturities
Long-term debt	501,000,000			502,000,000
Debt Information [Abstract]
Face amount	$ 500,000,000
Effective interest rate	2.875%	2.875%	2.875%
Senior notes | Senior notes due 2021
Long-term debt, net of current maturities
Long-term debt	$ 497,000,000			646,000,000
Debt Information [Abstract]
Face amount	500,000,000
Senior notes | Senior notes due 2023
Long-term debt, net of current maturities
Long-term debt	277,000,000			278,000,000
Debt Information [Abstract]
Face amount	$ 274,000,000
Effective interest rate	4.45%	4.45%	4.45%
Senior notes | Senior notes due 2023
Long-term debt, net of current maturities
Long-term debt	$ 172,000,000			173,000,000
Debt Information [Abstract]
Face amount	$ 171,000,000
Effective interest rate	4.45%	4.45%	4.45%
Senior notes | Senior notes due 2025
Long-term debt, net of current maturities
Long-term debt	$ 507,000,000			507,000,000
Debt Information [Abstract]
Face amount	$ 500,000,000
Effective interest rate	4.25%	4.25%	4.25%
Senior notes | Senior notes due 2025
Long-term debt, net of current maturities
Long-term debt	$ 315,000,000			346,000,000
Debt Information [Abstract]
Face amount | £		£ 250,000,000
Effective interest rate	2.75%	2.75%	2.75%
Senior notes | Senior notes due 2026
Long-term debt, net of current maturities
Long-term debt	$ 738,000,000			0
Debt Information [Abstract]
Face amount | €			€ 650,000,000
Effective interest rate	1.75%	1.75%	1.75%
Senior notes | Senior notes due 2028
Long-term debt, net of current maturities
Long-term debt	$ 509,000,000			509,000,000
Debt Information [Abstract]
Face amount	$ 500,000,000
Effective interest rate	4.75%	4.75%	4.75%
Senior notes | Senior notes due 2030
Long-term debt, net of current maturities
Long-term debt	$ 275,000,000			277,000,000
Debt Information [Abstract]
Face amount	$ 234,000,000
Effective interest rate	7.45%	7.45%	7.45%
Secured debt | Lease credit facility
Long-term debt, net of current maturities
Long-term debt	$ 30,000,000			46,000,000
Capitalized lease liabilities
Long-term debt, net of current maturities
Long-term debt	1,182,000,000			1,235,000,000
Borrowings for assets acquired under long-term financing
Long-term debt, net of current maturities
Long-term debt	451,000,000			405,000,000
Mandatorily redeemable preferred stock outstanding
Long-term debt, net of current maturities
Long-term debt	$ 62,000,000			61,000,000
Debt Information [Abstract]
Effective interest rate	6.00%	6.00%	6.00%
Other borrowings
Long-term debt, net of current maturities
Long-term debt	$ 110,000,000			$ 113,000,000
Minimum | Term loan | AUD term loan
Debt Information [Abstract]
Weighted average interest rate, short- term debt	2.90%	2.90%	2.90%
Minimum | Term loan | USD term loan
Debt Information [Abstract]
Weighted average interest rate, short- term debt	3.10%	3.10%	3.10%
Minimum | Senior notes | Senior notes due 2021
Debt Information [Abstract]
Effective interest rate	3.00%	3.00%	3.00%
Minimum | Secured debt | Lease credit facility
Debt Information [Abstract]
Weighted average interest rate, short- term debt	2.80%	2.80%	2.80%
Minimum | Capitalized lease liabilities
Debt Information [Abstract]
Weighted average interest rate, short- term debt	1.00%	1.00%	1.00%
Minimum | Borrowings for assets acquired under long-term financing
Debt Information [Abstract]
Weighted average interest rate, short- term debt	2.30%	2.30%	2.30%
Minimum | Other borrowings
Debt Information [Abstract]
Weighted average interest rate, short- term debt	0.50%	0.50%	0.50%
Maximum | Term loan | GBP term loan
Debt Information [Abstract]
Effective interest rate	1.50%	1.50%	1.50%
Maximum | Term loan | AUD term loan
Debt Information [Abstract]
Weighted average interest rate, short- term debt	3.30%	3.30%	3.30%
Maximum | Term loan | USD term loan
Debt Information [Abstract]
Weighted average interest rate, short- term debt	3.30%	3.30%	3.30%
Maximum | Senior notes | Senior notes due 2021
Debt Information [Abstract]
Effective interest rate	3.30%	3.30%	3.30%
Maximum | Secured debt | Lease credit facility
Debt Information [Abstract]
Weighted average interest rate, short- term debt	3.50%	3.50%	3.50%
Maximum | Capitalized lease liabilities
Debt Information [Abstract]
Weighted average interest rate, short- term debt	12.00%	12.00%	12.00%
Maximum | Borrowings for assets acquired under long-term financing
Debt Information [Abstract]
Weighted average interest rate, short- term debt	4.10%	4.10%	4.10%
Maximum | Other borrowings
Debt Information [Abstract]
Weighted average interest rate, short- term debt	7.40%	7.40%	7.40%
LIBOR | Term loan | GBP term loan
Debt Information [Abstract]
Basis spread on variable rate	0.65%
LIBOR | Term loan | GBP term loan
Debt Information [Abstract]
Basis spread on variable rate	0.80%
LIBOR | Minimum | Term loan | AUD term loan
Debt Information [Abstract]
Basis spread on variable rate	0.60%
LIBOR | Minimum | Term loan | AUD term loan
Debt Information [Abstract]
Basis spread on variable rate	0.95%
LIBOR | Maximum | Term loan | AUD term loan
Debt Information [Abstract]
Basis spread on variable rate	0.95%
LIBOR | Maximum | Term loan | AUD term loan
Debt Information [Abstract]
Basis spread on variable rate	1.45%
EURIBOR | Term loan | EUR term loan
Debt Information [Abstract]
Basis spread on variable rate	1.75%
Eurocurrency Rate | Minimum | Term loan | EUR term loan
Debt Information [Abstract]
Basis spread on variable rate	0.75%
Eurocurrency Rate | Minimum | Term loan | USD term loan
Debt Information [Abstract]
Basis spread on variable rate	1.00%
Eurocurrency Rate | Maximum | Term loan | EUR term loan
Debt Information [Abstract]
Basis spread on variable rate	1.35%
Eurocurrency Rate | Maximum | Term loan | USD term loan
Debt Information [Abstract]
Basis spread on variable rate	1.75%
Base Rate | Minimum | Term loan | USD term loan
Debt Information [Abstract]
Basis spread on variable rate	0.00%
Base Rate | Maximum | Term loan | USD term loan
Debt Information [Abstract]
Basis spread on variable rate	0.75%
Three-month LIBOR | Senior notes | Senior notes due 2021
Debt Information [Abstract]
Basis spread on variable rate	0.95%
Commercial paper
Debt Information [Abstract]
Maximum borrowing capacity | €			€ 1,000,000,000
Commercial paper | Minimum
Debt Information [Abstract]
Weighted average interest rate, short- term debt	(0.10%)	(0.10%)	(0.10%)
Commercial paper | Maximum
Debt Information [Abstract]
Weighted average interest rate, short- term debt	0.02%	0.02%	0.02%
Capital lease obligations, current portion | Minimum
Debt Information [Abstract]
Weighted average interest rate, short- term debt	1.00%	1.00%	1.00%
Capital lease obligations, current portion | Maximum
Debt Information [Abstract]
Weighted average interest rate, short- term debt	12.00%	12.00%	12.00%