Intangible Assets - Summary of Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Mar. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 1,622	$ 995
Accumulated Amortization	181	98
Net Carrying Value	1,441	897
Program assets
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1,400	900
Accumulated Amortization	117	69
Net Carrying Value	1,283	831
Software
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	80	75
Accumulated Amortization	44	28
Net Carrying Value	36	47
Developed technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	105
Accumulated Amortization	8
Net Carrying Value	97
Backlog
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	16
Accumulated Amortization	5
Net Carrying Value	11
Outsourcing contract costs
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	20	20
Accumulated Amortization	7	1
Net Carrying Value	13	$ 19
Favorable leases
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	1
Accumulated Amortization	0
Net Carrying Value	$ 1