Equity (Narrative) (Details) - USD ($) shares in Millions			9 Months Ended
	Aug. 05, 2016	Jan. 02, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Jun. 30, 2015	Dec. 01, 2014
Class of Stock [Line Items]
Cost of Treasury Stock Acquired			$ 1,339,000,000	$ 744,000,000
Class B Stock Held in Treasury
Class of Stock [Line Items]
Class B Stock held in treasury, at cost			770,000,000				$ 651,000,000
Class B Stock Held in Treasury | Retained Earnings
Class of Stock [Line Items]
Stockholders' Equity, Period Increase (Decrease)		$ (484,000,000)	$ (119,000,000)
Class B Stock Held in Treasury | Additional Paid-in Capital
Class of Stock [Line Items]
Stockholders' Equity, Period Increase (Decrease)		$ (167,000,000)
Under December 2015 Board Of Directors Authorization
Class of Stock [Line Items]
Amount of Stock Repurchases Authorized by the Board of Directors					$ 1,500,000,000.0
Under June 2015 Board Of Directors Authorization
Class of Stock [Line Items]
Amount of Stock Repurchases Authorized by the Board of Directors						$ 1,000,000,000.0
Under August 2016 Board of Director Authorization
Class of Stock [Line Items]
Amount of Stock Repurchases Authorized by the Board of Directors	$ 2,000,000,000.0
Stock Repurchase Program, Increase (Decrease) In Authorized Amount	$ 500,000,000
Under August 2016 Board of Director Authorization | Common Stock
Class of Stock [Line Items]
Number of Treasury Stock Shares Acquired			18.5
Cost of Treasury Stock Acquired			$ 1,375,000,000