Income Taxes - Narrative (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
	Mar. 01, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2017	Mar. 31, 2015
Income Tax Contingency [Line Items]
Income tax expense				$ (53)	$ 1,614	$ 908
Income tax rates (percent)				22.20%	23.40%	27.90%
Statutory federal income tax rate (percent)				31.60%	35.00%	35.00%
Research and development credit				$ 11
Transition tax on foreign earnings				457	$ 0	$ 0
Goodwill impairment charge				1,738	290	0
Net tax benefit on intellectual property transfer				178	137	0
Tax expense recognized on gain from asset exchange	$ 929
Tax benefit related to adoption of amended accounting guidance				8	54	0
Net discrete tax expense (benefit)						(19)
Discrete tax benefit						25
Valuation allowance		$ 751		751	503
Increase in valuation allowance				248
Unrecognized tax benefits		1,183		1,183	486	555		$ 616
Unrecognized tax benefits that would Impact income tax expense and the effective tax rate		1,042		1,042
Income tax expense (benefit), before any tax effect, related to accrued interest and penalties				(1)	(6)	12
Accrued interest and penalties on unrecognized tax benefits		37		37	45
Tax benefit resulting from favorable resolution of various uncertain tax positions			$ 39	7	113	$ 141
Provisional net tax benefit		68		1,324
Provisional tax expense resulting from the 2017 Tax Act		23		457
Undistributed earnings of foreign operations							$ 5,854
Federal
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards		111		111
State
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards		2,787		2,787
Foreign Tax Authority
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards		1,806		1,806
Capital loss carryforwards		$ 756		756
Technology Solutions
Income Tax Contingency [Line Items]
Goodwill impairment charge				0	290
New Accounting Pronouncement, Early Adoption, Effect
Income Tax Contingency [Line Items]
Tax benefit related to adoption of amended accounting guidance				$ 8	$ 54