Restructuring - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended		13 Months Ended
	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2015
Restructuring Cost and Reserve [Line Items]
Pre-tax charge	$ 229	$ 14	$ 229
Severance and employee related costs			207
Reserve balance	222	106	222	$ 106	$ 0
Other Accrued Liabilities
Restructuring Cost and Reserve [Line Items]
Reserve balance	172	71	172	71
Other Noncurrent Assets/Liabilities
Restructuring Cost and Reserve [Line Items]
Reserve balance	50	35	50	35
Reduction in Workforce
Restructuring Cost and Reserve [Line Items]
Severance and employee related costs			117
Business Process Initiatives
Restructuring Cost and Reserve [Line Items]
Severance and employee related costs			$ 90
Cost Alignment Plan [Member]
Restructuring Cost and Reserve [Line Items]
Pre-tax charges recorded to-date				243
Pre-tax charge	$ 229
Cost Alignment Plan [Member] | Minimum
Restructuring Cost and Reserve [Line Items]
Expected total pre-tax charges		250		250
Cost Alignment Plan [Member] | Maximum
Restructuring Cost and Reserve [Line Items]
Expected total pre-tax charges		$ 270		$ 270