Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders' Equity Note [Abstract]
Dividends per common share (in dollars per share)	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.12	$ 0.12	$ 0.6	$ 0.54	$ 0.48
Dividends									$ 293	$ 296	$ 295
Class B Common Stock purchased, value									$ 2,800
Average price per share repurchased (in dollars per share)									$ 54.18
Shares of Class B Common Stock repurchased									51,700,000
Remaining authorization under repurchase program	$ 2,000								$ 2,000
Minimum Class A shares needed for conversion	5,000								5,000
Conversion of A shares into B shares									100,000	1,300,000	4,000,000