Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income [Abstract]
Basic EPS									$ 2,400	$ 2,024	$ 2,441
Diluted EPS									$ 2,400	$ 2,024	$ 2,441
Shares [Abstract]
Basic EPS (in shares)									870,600,000	881,800,000	891,800,000
Stock options and restricted stock units (in shares)									2,400,000	6,000,000	6,600,000
Diluted EPS (in shares)									873,000,000	887,800,000	898,400,000
Earnings Per Share, Basic [Abstract]
Basic EPS (in dollars per share)	$ 0.70	$ 0.60	$ 0.73	$ 0.72	$ 0.37	$ 0.69	$ 0.59	$ 0.64	$ 2.76	$ 2.30	$ 2.74
Earnings Per Share, Diluted [Abstract]
Diluted EPS (in dollars per share)	$ 0.70	$ 0.60	$ 0.73	$ 0.72	$ 0.37	$ 0.68	$ 0.59	$ 0.64	$ 2.75	$ 2.28	$ 2.72
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)									18,039,961	11,056,725	3,187,485
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)									9,529	91	2,693