Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 1,626	$ 995
Accumulated Amortization	220	98
Net Carrying Value	1,406	897
Program assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1,400	900
Accumulated Amortization	145	69
Net Carrying Value	1,255	831
Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	83	75
Accumulated Amortization	47	28
Net Carrying Value	36	47
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	105
Accumulated Amortization	13
Net Carrying Value	92
Backlog
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	16
Accumulated Amortization	9
Net Carrying Value	7
Outsourcing contract costs
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	21	20
Accumulated Amortization	6	1
Net Carrying Value	15	$ 19
Favorable leases
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1
Accumulated Amortization	0
Net Carrying Value	$ 1