Recently Issued Accounting Pronouncements (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in weighted-average dilutive shares outstanding (in shares)	750	735	748	734
Change in diluted earnings per share (in dollars per share)	$ 0.17	$ 0.29	$ 0.61	$ 0.81
Pro Forma | New Accounting Pronouncement, Early Adoption, Effect [Member] | Potential Adjustments For ASU 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Windfall tax benefits as a reduction to income tax expense	$ 24		$ 51
Increase in weighted-average dilutive shares outstanding (in shares)	3		3
Change in diluted earnings per share (in dollars per share)	$ 0.03		$ 0.07
Increase in net cash provided by operating activities			$ 52
Decrease in net cash provided by (used in) financing activities			$ (52)