Quarterly Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 13,011	$ 12,480	$ 12,646	$ 12,451	$ 10,962	$ 10,678	$ 10,403	$ 9,866	$ 50,588	$ 41,909	$ 41,541
Net income from continuing operations applicable to common shareholders	1,111	183	1,399	2,385	2,244	1,189	1,080	801	5,078	5,314	4,158
Income (loss) from discontinued operations, net of tax	(321)	325	196	(3,793)	354	(63)	144	(288)	(3,593)	147	520
Net income (loss) applicable to common shareholders	$ 790	$ 508	$ 1,595	$ (1,408)	$ 2,598	$ 1,126	$ 1,224	$ 513	$ 1,485	$ 5,461	$ 4,678
Basic
Continuing operations (in dollars per share)	$ 3.90	$ 0.62	$ 4.68	$ 7.88	$ 7.38	$ 3.82	$ 3.44	$ 2.52	$ 17.23	$ 17.06	$ 12.67
Discontinued operations (in dollars per share)	(1.13)	1.11	0.66	(12.53)	1.16	(0.20)	0.46	(0.90)	(12.19)	0.47	1.58
Earnings per common share - Basic (in dollars per share)	2.77	1.73	5.34	(4.65)	8.54	3.62	3.90	1.62	5.04	17.53	14.25
Diluted
Continuing operations (in dollars per share)	3.84	0.62	4.61	7.78	7.30	3.78	3.41	2.48	16.98	16.84	12.47
Discontinued operations (in dollars per share)	(1.11)	1.09	0.65	(12.38)	1.15	(0.20)	0.45	(0.89)	(12.02)	0.47	1.56
Earnings per common share - Diluted (in dollars per share)	$ 2.73	$ 1.71	$ 5.26	$ (4.60)	$ 8.45	$ 3.58	$ 3.86	$ 1.59	$ 4.96	$ 17.31	$ 14.03