Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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
Earnings Per Share [Abstract]
Shareholders' net income	$ 977	$ 1,351	$ 1,408	$ 1,368	$ 144	$ 772	$ 806	$ 915	$ 5,104	$ 2,637	$ 2,237
Shares:
Weighted average									375,919	246,652	250,892
Common stock equivalents									3,898	3,573	4,180
Total shares									379,817	250,225	255,072
EPS, basic	$ 2.63	$ 3.60	$ 3.73	$ 3.61	$ 0.56	$ 3.18	$ 3.32	$ 3.78	$ 13.58	$ 10.69	$ 8.92
EPS, effect of dilution									(0.14)	(0.15)	(0.15)
EPS, diluted	$ 2.60	$ 3.57	$ 3.70	$ 3.56	$ 0.55	$ 3.14	$ 3.29	$ 3.72	$ 13.44	$ 10.54	$ 8.77
Employee Stock Option [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive options									3,500	900	900