Share-Based Compensation (Stock Option Activity) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Share-based Compensation [Abstract]
Stock options outstanding	5		6
Stock options granted	1
Stock options exercised	(2)
Stock options vested and expected to vest	5	[1]
Stock options vested and exercisable	2
Stock options outstanding, weighted-average exercise price	$ 95.01		$ 78.07
Stock options granted, weighted-average exercise price	$ 184.84
Stock options exercised, weighted-average exercise price	$ 67.64
Stock options vested and expected to vest, exercise price	$ 95.01	[1]
Stock options vested and exercisable, exercise price	$ 69.27
Stock options outstanding, remaining contractual term	4 years		4 years
Stock options vested and expected to vest, remaining contractual term	4 years	[1]
Stock options vested and exercisable, remaining contractual term	3 years
Stock options outstanding, intrinsic value	$ 539	[2]	$ 473	[2]
Stock options vested and expected to vest, intrinsic value	538	[1],[2]
Stock options vested and exercisable, intrinsic value	$ 363	[2]

[1] The number of options expected to vest takes into account an estimate of expected forfeitures.

[2] The intrinsic value is calculated as the difference between the period-end market price of the Company’s common stock and the exercise price of “in-the-money” options.