Stockholders' Equity - Earnings per Share (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
As reported shares	934	909	925	910
Effect of options and performance share award units	6	3	6	4
Diluted shares	940	912	931	914
Stock options and performance share award units that were not included in the diluted earnings per share calculation (in shares)	0	15	0	1