Stockholders' Equity (Share Repurchase Program) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	5 Months Ended		6 Months Ended	12 Months Ended			23 Months Ended
	Feb. 28, 2013	Dec. 31, 2014	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Jul. 28, 2015	Jan. 21, 2015	Jan. 31, 2014	Dec. 31, 2012
Equity, Class of Treasury Stock [Line Items]
Payments for Repurchase of Common Stock					$ 2,353	$ 2,000	$ 1,000
Repurchased and retired, shares					39,564,000	30,110,000	20,400,000
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
Payments for Repurchase of Common Stock					$ 2,000
Repurchased and retired, shares					35,000,000
Accelerated Share Repurchases, Final Price Paid Per Share					$ 57.16
January 2014 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, authorized amount											$ 5,000
Payments for Repurchase of Common Stock			$ 1,000					$ 2,353
Repurchased and retired, shares			15,100,000					34,700,000
August 2014 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Payments for Repurchase of Common Stock		$ 700
Repurchased and retired, shares		10,400,000
Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Payments for Repurchase of Common Stock					$ 353	$ 300
Repurchased and retired, shares					4,600,000	4,700,000
December 2012 Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, authorized amount												$ 1,000
Payments for Repurchase of Common Stock	$ 1,000
Repurchased and retired, shares				20,400,000