Stockholders' Equity (Share Repurchase Program) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		14 Months Ended	1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2015	Jan. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Payments for repurchase of common stock	$ 282	$ 1,061
January 2014 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, Authorized Amount					5,000
Repurchased and retired, shares			33.7
Payments for repurchase of common stock			$ 2,282
Q1 2015 Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased and retired, shares				3.6