Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Income Tax Contingency [Line Items]
Income tax expense	$ 908,000,000	$ 815,000,000	$ 757,000,000
Net discrete tax expense (benefit)	$ (42,000,000)	$ (33,000,000)	$ 94,000,000
Income tax rates	27.90%	30.70%	34.90%
Undistributed earnings of foreign operations	$ 5,831,000,000
Deferred tax liability	0
Valuation allowance	267,000,000	$ 229,000,000
Increase in valuation allowance	38,000,000
Unrecognized tax benefits	555,000,000	616,000,000	$ 647,000,000	$ 560,000,000
Unrecognized tax benefits that would Impact income tax expense and the effective tax rate	380,000,000
Potential reduction of unrecognized benefits due to audit resolutions and expiration of statutes of limitations (up to)	125,000,000
Income tax expense (benefit), before any tax effect, related to accrued interest and penalties	12,000,000	(24,000,000)	48,000,000
Accrued interest and penalties on unrecognized tax benefits	77,000,000	122,000,000
Foreign Tax Authority
Income Tax Contingency [Line Items]
Net discrete tax expense (benefit)	(19,000,000)
Federal, state and foreign net operating loss carryforwards	889,000,000
Tax Reserve
Income Tax Contingency [Line Items]
Net discrete tax expense (benefit)	(25,000,000)
IRS
Income Tax Contingency [Line Items]
Net discrete tax expense (benefit)		$ (55,000,000)
Canada Revenue Agency
Income Tax Contingency [Line Items]
Net discrete tax expense (benefit)	(8,000,000)		$ 122,000,000
Federal
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards	35,000,000
State
Income Tax Contingency [Line Items]
Federal, state and foreign net operating loss carryforwards	$ 1,790,000,000