Segment Information - Segment Measures (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 4,554	$ 4,851	$ 9,056	$ 9,741
Segment profit	283	529	473	1,181
Depreciation and amortization	373	316	717	648
Amortization of acquired intangible assets	152	151	300	289
Operating segments
Segment Reporting Information [Line Items]
Revenues	4,554	4,851	9,056	9,741
Segment profit	353	602	591	1,308
Depreciation and amortization	350	291	667	594
Operating segments | GBS
Segment Reporting Information [Line Items]
Revenues	2,242	2,285	4,416	4,444
Segment profit	317	359	532	725
Depreciation and amortization	59	39	109	67
Operating segments | GIS
Segment Reporting Information [Line Items]
Revenues	2,312	2,566	4,640	5,297
Segment profit	36	243	59	583
Depreciation and amortization	291	252	558	527
All Other
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment profit	(70)	(73)	(118)	(127)
Depreciation and amortization	$ 23	$ 25	$ 50	$ 54