Income Taxes (Details) - USD ($)	3 Months Ended				6 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax [Line Items]
Income tax expense related to continuing operations	$ 244,000,000		$ 223,000,000		$ 500,000,000	$ 408,000,000
Net discrete tax benefits	$ 24,000,000		$ 6,000,000		$ 29,000,000	$ 18,000,000
Income tax rate (as a percent)	27.70%		31.20%		28.80%	31.00%
Discrete tax benefit	$ 25,000,000
Unrecognized tax benefits	548,000,000	$ 497,000,000			$ 548,000,000
Unrecognized tax benefits that would reduce income tax expense and the effective tax rate	374,000,000	337,000,000			374,000,000
Significant change in unrecognized tax benefits is reasonably possible, amount of unrecorded benefit	124,000,000				124,000,000
Income tax expense (benefit)	(1,000,000)		$ 3,000,000		5,000,000	$ 7,000,000
Accrued interest and penalties on unrecognized tax benefits	$ 75,000,000		$ 161,000,000		$ 75,000,000	$ 161,000,000
IRS
Income Tax [Line Items]
Net discrete tax benefits				$ 17,000,000
CRA
Income Tax [Line Items]
Income tax expense to settle transfer pricing		$ 12,000,000