Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income [Abstract]
Basic EPS									$ 2,367	$ 2,400	$ 2,024
Diluted EPS									$ 2,367	$ 2,400	$ 2,024
Shares [Abstract]
Basic EPS (in shares)									859,100,000	870,600,000	881,800,000
Stock options and restricted stock units (in shares)									2,000,000.0	2,400,000	6,000,000.0
Diluted EPS (in shares)									861,100,000	873,000,000.0	887,800,000
Earnings Per Share, Basic [Abstract]
Basic EPS (in dollars per share)	$ 0.75	$ 0.67	$ 0.68	$ 0.65	$ 0.70	$ 0.60	$ 0.73	$ 0.72	$ 2.76	$ 2.76	$ 2.30
Earnings Per Share, Diluted [Abstract]
Diluted EPS (in dollars per share)	$ 0.75	$ 0.67	$ 0.68	$ 0.65	$ 0.70	$ 0.60	$ 0.73	$ 0.72	$ 2.75	$ 2.75	$ 2.28
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)									19,901,202	18,039,961	11,056,725
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)									4,516	9,529	91