Capital Leases - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Leases [Abstract]
Capital lease assets, net	$ 346,000,000		$ 346,000,000		$ 274,000,000
Capital lease, accumulated depreciation	99,000,000		99,000,000		57,000,000
Depreciation of capital lease assets	29,000,000	$ 21,000,000	76,000,000	$ 51,000,000
Capital lease obligations	289,000,000		289,000,000		$ 304,000,000
Interest expense on capital leases	$ 5,000,000	$ 0	$ 14,000,000	$ 7,000,000