Stockholders' Equity (Share Repurchase Program) (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		15 Months Ended	26 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2016	Jul. 28, 2015	Jan. 21, 2015	Jan. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock	$ 0	$ 282
January 2014 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, Authorized Amount							$ 5,000
Repurchased and retired, shares	0.0			34.7
Repurchase of common stock	$ 0			$ 2,353
YTD 2015 Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased and retired, shares		3.6
Repurchase of common stock		$ 282
2015 Share Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
2015 Share buyback announcement						$ 4,000
Share buyback plan, Authorized Amount					$ 2,000
Repurchased and retired, shares	0.0		35.0
Repurchase of common stock	$ 0		$ 2,000