Debt - Schedule of Debt (Details)	9 Months Ended	12 Months Ended
	Dec. 31, 2019	Mar. 31, 2020 USD ($)	Mar. 31, 2020 EUR (€)	Mar. 31, 2020 GBP (£)	Mar. 31, 2019 USD ($)
Short-term debt and current maturities of long-term debt
Commercial paper		$ 542,000,000			$ 694,000,000
Current maturities of long-term debt		290,000,000			766,000,000
Current maturities of capitalized lease liabilities		444,000,000
Current maturities of capitalized lease liabilities					482,000,000
Short-term debt and current maturities of long-term debt		1,276,000,000			1,942,000,000
Long-term debt, net of current maturities
Finance lease liabilities		1,046,000,000
Finance lease liabilities					1,127,000,000
Long-term debt		9,406,000,000			6,718,000,000
Less: current maturities		734,000,000			1,248,000,000
Long-term debt, net of current maturities		8,672,000,000			5,470,000,000
Borrowings for assets acquired under long-term financing
Long-term debt, net of current maturities
Long-term debt, net of current maturities		802,000,000			462,000,000
Mandatorily redeemable preferred stock outstanding
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 62,000,000			62,000,000
Debt Information [Abstract]
Effective interest rate		6.00%	6.00%	6.00%
Other borrowings
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 70,000,000			109,000,000
AUD term loan | Loans payable
Long-term debt, net of current maturities
Long-term debt, net of current maturities		489,000,000			567,000,000
GBP term loan | Loans payable
Long-term debt, net of current maturities
Long-term debt, net of current maturities		556,000,000			583,000,000
EUR term loan | Loans payable
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 822,000,000			0
Debt Information [Abstract]
Effective interest rate		0.65%	0.65%	0.65%
EUR term loan | Loans payable
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 821,000,000			0
Debt Information [Abstract]
Effective interest rate		0.80%	0.80%	0.80%
USD term loan | Loans payable
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 480,000,000			0
$500 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 0			502,000,000
Debt Information [Abstract]
Effective interest rate		2.88%	2.88%	2.88%
Face amount		$ 500,000,000
$500 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long-term debt, net of current maturities		0			498,000,000
Debt Information [Abstract]
Face amount		500,000,000
$274 million Senior notes | Senior notes
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 276,000,000			277,000,000
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, net of current maturities		$ 172,000,000			172,000,000
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, net of current maturities		$ 505,000,000			506,000,000
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, net of current maturities		$ 307,000,000			322,000,000
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, net of current maturities		$ 709,000,000			725,000,000
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, net of current maturities		$ 507,000,000			508,000,000
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, net of current maturities		$ 271,000,000			273,000,000
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, net of current maturities		$ 11,000,000			25,000,000
7.4% USD Senior note | Senior notes
Debt Information [Abstract]
Stated interest rate		7.40%	7.40%	7.40%
Minimum | Finance lease liabilities
Debt Information [Abstract]
Effective interest rate		0.62%	0.62%	0.62%
Minimum | Borrowings for assets acquired under long-term financing
Debt Information [Abstract]
Effective interest rate		0.48%	0.48%	0.48%
Minimum | AUD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate		1.65%	1.65%	1.65%
Minimum | GBP term loan | Loans payable
Debt Information [Abstract]
Effective interest rate		1.50%	1.50%	1.50%
Minimum | USD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate		2.85%	2.85%	2.85%
Minimum | $500 million Senior notes | Senior notes
Debt Information [Abstract]
Effective interest rate		3.08%	3.08%	3.08%
Minimum | Lease credit facility | Secured debt
Debt Information [Abstract]
Effective interest rate		1.70%	1.70%	1.70%
Maximum | Finance lease liabilities
Debt Information [Abstract]
Effective interest rate		17.68%	17.68%	17.68%
Maximum | Borrowings for assets acquired under long-term financing
Debt Information [Abstract]
Effective interest rate		5.78%	5.78%	5.78%
Maximum | AUD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate		2.66%	2.66%	2.66%
Maximum | GBP term loan | Loans payable
Debt Information [Abstract]
Effective interest rate		1.63%	1.63%	1.63%
Maximum | USD term loan | Loans payable
Debt Information [Abstract]
Effective interest rate		3.67%	3.67%	3.67%
Maximum | $500 million Senior notes | Senior notes
Debt Information [Abstract]
Effective interest rate		3.69%	3.69%	3.69%
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		(0.23%)	(0.23%)	(0.23%)
Euro-denominated commercial paper | Maximum
Debt Information [Abstract]
Weighted average interest rate		2.76%	2.76%	2.76%
Current maturities of capitalized lease liabilities | Minimum
Debt Information [Abstract]
Effective interest rate		0.62%	0.62%	0.62%
Current maturities of capitalized lease liabilities | Maximum
Debt Information [Abstract]
Effective interest rate		17.68%	17.68%	17.68%
Bank Bill Swap Rate | Minimum | AUD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.60%
Bank Bill Swap Rate | Maximum | AUD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.95%
Three-month LIBOR | GBP term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate	0.80%
EURIBOR | Minimum | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate		0.40%
EURIBOR | Minimum | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate		0.55%
EURIBOR | Minimum | USD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate		1.00%
EURIBOR | Maximum | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate		0.90%
EURIBOR | Maximum | EUR term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate		1.05%
EURIBOR | Maximum | USD term loan | Loans payable
Debt Information [Abstract]
Basis spread on variable rate		1.50%
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		0.50%
Revolving credit facility | Line of credit
Long-term debt, net of current maturities
Long-term debt, net of current maturities		$ 1,500,000,000			$ 0
Debt Information [Abstract]
Effective interest rate		2.06%	2.06%	2.06%