Debt - Schedule of Debt (Details)	12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2019 GBP (£)	Mar. 31, 2019 EUR (€)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 EUR (€)
Short-term debt and current maturities of long-term debt
Short term debt	$ 694,000,000			$ 863,000,000
Current maturities of long-term debt	766,000,000			439,000,000
Current maturities of capitalized lease liabilities	482,000,000			616,000,000
Short-term debt and current maturities of long-term debt	1,942,000,000			1,918,000,000
Long-term debt, net of current maturities
Long term debt	6,718,000,000			7,147,000,000
Less: current maturities	1,248,000,000			1,055,000,000
Long-term debt, net of current maturities	5,470,000,000			6,092,000,000
Capitalized lease liabilities
Long-term debt, net of current maturities
Long term debt	1,127,000,000			1,235,000,000
Borrowings for assets acquired under long-term financing
Long-term debt, net of current maturities
Long term debt	462,000,000			405,000,000
Mandatorily redeemable preferred stock outstanding, due March 2023
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	$ 109,000,000			113,000,000
GBP term loan | Loans payable
Long-term debt, net of current maturities
Long term debt	0			260,000,000
EUR term loan | Loans payable
Long-term debt, net of current maturities
Long term debt	0			493,000,000
AUD term loan | Loans payable
Long-term debt, net of current maturities
Long term debt	567,000,000			0
AUD term loan | Loans payable
Long-term debt, net of current maturities
Long term debt	0			210,000,000
GBP term loan | Loans payable
Long-term debt, net of current maturities
Long term debt	583,000,000			0
EUR term loan | Loans payable
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%
USD term loan | Loans payable
Long-term debt, net of current maturities
Long term debt	$ 0			899,000,000
$500 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 502,000,000			502,000,000
Debt Information [Abstract]
Effective interest rate	2.875%	2.875%	2.875%
Face amount	$ 500,000,000
$500 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	498,000,000			646,000,000
Debt Information [Abstract]
Face amount	500,000,000
$274 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 277,000,000			278,000,000
Debt Information [Abstract]
Effective interest rate	4.45%	4.45%	4.45%
Face amount	$ 274,000,000
$171 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 172,000,000			173,000,000
Debt Information [Abstract]
Effective interest rate	4.45%	4.45%	4.45%
Face amount	$ 171,000,000
$500 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 506,000,000			507,000,000
Debt Information [Abstract]
Effective interest rate	4.25%	4.25%	4.25%
Face amount	$ 500,000,000
£250 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 322,000,000			346,000,000
Debt Information [Abstract]
Effective interest rate	2.75%	2.75%	2.75%
Face amount | £		£ 250,000,000
€650 million Senior Notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 725,000,000			0
Debt Information [Abstract]
Effective interest rate	1.75%	1.75%	1.75%
Face amount | €			€ 650,000,000
$500 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 508,000,000			509,000,000
Debt Information [Abstract]
Effective interest rate	4.75%	4.75%	4.75%
Face amount	$ 500,000,000
$234 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long term debt	$ 273,000,000			277,000,000
Debt Information [Abstract]
Effective interest rate	7.45%	7.45%	7.45%
Face amount	$ 234,000,000
Lease credit facility | Secured debt
Long-term debt, net of current maturities
Long term debt	$ 25,000,000			$ 46,000,000
Minimum | Capitalized lease liabilities
Debt Information [Abstract]
Effective interest rate	1.00%	1.00%	1.00%
Minimum | Borrowings for assets acquired under long-term financing
Debt Information [Abstract]
Effective interest rate	2.30%	2.30%	2.30%
Minimum | Other borrowings
Debt Information [Abstract]
Effective interest rate	0.50%	0.50%	0.50%
Minimum | GBP term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	1.30%	1.30%	1.30%
Minimum | AUD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	2.70%	2.70%	2.70%
Minimum | AUD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	2.90%	2.90%	2.90%
Minimum | USD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	3.10%	3.10%	3.10%
Minimum | $500 million Senior notes | Loans payable
Debt Information [Abstract]
Effective interest rate	3.00%	3.00%	3.00%
Minimum | Lease credit facility | Secured debt
Debt Information [Abstract]
Effective interest rate	2.20%	2.20%	2.20%
Maximum | Capitalized lease liabilities
Debt Information [Abstract]
Effective interest rate	12.00%	12.00%	12.00%
Maximum | Borrowings for assets acquired under long-term financing
Debt Information [Abstract]
Effective interest rate	4.50%	4.50%	4.50%
Maximum | Other borrowings
Debt Information [Abstract]
Effective interest rate	7.40%	7.40%	7.40%
Maximum | GBP term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	1.50%	1.50%	1.50%
Maximum | AUD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	2.90%	2.90%	2.90%
Maximum | AUD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	3.30%	3.30%	3.30%
Maximum | USD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate	3.30%	3.30%	3.30%
Maximum | $500 million Senior notes | Loans payable
Debt Information [Abstract]
Effective interest rate	3.80%	3.80%	3.80%
Maximum | Lease credit facility | Secured debt
Debt Information [Abstract]
Effective interest rate	3.50%	3.50%	3.50%
Euro-denominated commercial paper
Debt Information [Abstract]
Amount of multi-year committed revolving credit facility | €					€ 1,000,000,000
Euro-denominated commercial paper | Minimum
Debt Information [Abstract]
Weighted average interest rate	(0.10%)	(0.10%)	(0.10%)
Euro-denominated commercial paper | Maximum
Debt Information [Abstract]
Weighted average interest rate	0.02%	0.02%	0.02%
Capital Lease Obligations | Minimum
Debt Information [Abstract]
Effective interest rate	1.00%	1.00%	1.00%
Capital Lease Obligations | Maximum
Debt Information [Abstract]
Effective interest rate	12.00%	12.00%	12.00%
LIBOR | GBP term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.65%
EURIBOR | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	1.75%
Bank Bill Swap Bid Rate | Minimum | AUD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.60%
Bank Bill Swap Bid Rate | Minimum | AUD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.95%
Bank Bill Swap Bid Rate | Maximum | AUD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.95%
Bank Bill Swap Bid Rate | Maximum | AUD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	1.45%
Eurocurrency Rate | Minimum | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.75%
Eurocurrency Rate | Minimum | USD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	1.00%
Eurocurrency Rate | Maximum | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	1.35%
Eurocurrency Rate | Maximum | USD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	1.75%
Base rate | Minimum | USD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.00%
Base rate | Maximum | USD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.75%
Three-month LIBOR | GBP term loan | Senior notes
Debt Information [Abstract]
Basis spread on variable rate	0.80%
Three-month LIBOR | $500 million Senior notes | Senior notes
Debt Information [Abstract]
Basis spread on variable rate	0.95%