Common Stock (Accelerated Share Repurchase) (Details) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Jun. 30, 2015	Apr. 30, 2015	Dec. 31, 2015	Apr. 06, 2015
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount		$ 1,500
Payments for Repurchase of Common Stock		$ 1,500	$ 1,500
Delivered shares from Dealers	3.2	16.6	19.8
Fair Market Value of Delivered Shares	$ 225	$ 1,275	$ 1,500
Percentage of ASR common stock received				85.00%
Accelerated Share Repurchases, Final Price Paid Per Share			$ 75.75
Goldman Sachs [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock		750
JPMorgan Chase [Member]
Accelerated Share Repurchases [Line Items]
Payments for Repurchase of Common Stock		$ 750