Stock-Based Compensation Schedule of Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended		29 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016
May 2014 Repurchase Program [Member] [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 0	$ 0	$ 0	$ 57	$ 394
Stock Repurchased and Retired During Period, Shares	0.0	0.0	0.0	1.0	9.2
May 2015 Repurchase Program [Member] [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 127	$ 126	$ 256	$ 201
Stock Repurchased and Retired During Period, Shares	1.6	1.8	3.5	3.0
Repurchase Program, Total
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 127	$ 126	$ 256	$ 258
Stock Repurchased and Retired During Period, Shares	1.6	1.8	3.5	4.0