Stockholders' Equity (Share Repurchase Program) (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended		21 Months Ended	32 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2016	Jul. 28, 2015	Jan. 21, 2015	Jan. 31, 2014
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock		$ 416	$ 2,353
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	0.0			34.7
Repurchase of common stock	$ 0	$ 0			$ 2,353
YTD 2015 Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased and retired, shares			4.6
Repurchase of common stock			$ 353
2015 Share Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
2015 Share buyback announcement							$ 4,000
Repurchased and retired, shares	6.0	6.0		41.0
Repurchase of common stock	$ 416	$ 416		$ 2,416
Q3 2016 Open Market Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased and retired, shares	6.0
Repurchase of common stock	$ 416
By December 31, 2015 [Member] | 2015 Share Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, Authorized Amount						$ 2,000
By December 31, 2016 [Member] | 2015 Share Buyback Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Share buyback plan, Authorized Amount						$ 2,000