Stock-Based Compensation Schedule of Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	May 08, 2017	May 04, 2015
May 2015 Repurchase Program [Member] [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 31	$ 129
Stock Repurchase Program, Authorized Amount				$ 1,000
Stock Repurchased and Retired During Period, Shares	0.3	1.9
May 2017 Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 119	$ 0
Stock Repurchase Program, Authorized Amount			$ 1,200
Stock Repurchased and Retired During Period, Shares	1.1	0.0
Repurchase Program, Total
Equity, Class of Treasury Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 150	$ 129
Stock Repurchased and Retired During Period, Shares	1.4	1.9