Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income [Abstract]
Basic EPS									$ 2,441	$ 1,384	$ 2,180
Diluted EPS									$ 2,441	$ 1,384	$ 2,180
Shares [Abstract]
Basic EPS (in shares)									891,800,000	902,200,000	915,100,000
Stock options and restricted stock units (in shares)									6,600,000	7,500,000	9,200,000
Diluted EPS (in shares)									898,400,000	909,700,000	924,300,000
Earnings Per Share, Basic [Abstract]
Basic EPS (in dollars per share)	$ 0.68	$ 0.79	$ 0.67	$ 0.60	$ (0.51)	$ 0.81	$ 0.63	$ 0.60	$ 2.74	$ 1.53	$ 2.38
Earnings Per Share, Diluted [Abstract]
Diluted EPS (in dollars per share)	$ 0.68	$ 0.78	$ 0.67	$ 0.59	$ (0.51)	$ 0.80	$ 0.63	$ 0.59	$ 2.72	$ 1.52	$ 2.36
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)					6,600,000
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)									3,187,485	3,228,359	1,729,511
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)									2,693	120	2,311