Derivatives, Hedging Activities and Interest Expense - Derivative Activity Impact on Consolidated Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments Gain Loss [Line Items]
Interest expense on debt	$ 334	$ 304	$ 964	$ 923
Interest income on hedge accounting derivatives	(4)	(10)	(12)	(35)
Interest income on non-hedge accounting foreign currency swaps	(23)	(37)	(78)	(129)
Interest expense on non-hedge accounting interest rate swaps	28	30	86	94
Interest expense on debt and derivatives, net	335	287	960	853
Total interest expense	277	161	988	506
Interest expense [Member]
Derivative Instruments Gain Loss [Line Items]
(Gain) loss on non-hedge accounting foreign currency transactions	(222)	(567)	(68)	(1,354)
Loss (gain) on non-hedge accounting foreign currency swaps	263	542	170	1,253
(Gain) loss on non-hedge accounting interest rate swaps	(98)	(100)	(72)	(245)
Hedge accounting derivatives [Member] | Interest expense [Member]
Derivative Instruments Gain Loss [Line Items]
Loss on hedge accounting derivatives	6	55	23	128
Less hedged item: change in fair value of fixed rate debt	(7)	(56)	(25)	(129)
Ineffectiveness related to hedge accounting derivatives	(1)	(1)	(2)	(1)
Hedge accounting derivatives [Member] | Interest expense [Member] | Interest rate swap [Member]
Derivative Instruments Gain Loss [Line Items]
Loss on hedge accounting derivatives	0	5	0	15
Hedge accounting derivatives [Member] | Interest expense [Member] | Foreign currency swaps [Member]
Derivative Instruments Gain Loss [Line Items]
Loss on hedge accounting derivatives	$ 6	$ 50	$ 23	$ 113