Leases - Components of Lease Cost (Details) $ in Millions	3 Months Ended
	Jun. 30, 2019 USD ($)
Leases [Abstract]
Short-term lease cost	$ 8
Operating lease cost	115
Amortization of right-of-use assets	2
Interest on lease liabilities	1
Total finance lease cost	3
Variable lease cost	31
Sublease income	(8)
Total lease cost (2)	$ 149