Selected Quarterly Financial Data (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
Selected Quarterly Financial Information [Abstract]
Total revenues	$ 27,407	$ 26,674	$ 25,466	$ 24,666	$ 23,373	$ 23,251	$ 22,944	$ 22,537	$ 104,213	$ 92,105	$ 90,040
Income before income taxes	1,098	1,489	1,453	1,945	542	1,242	1,504	1,780	5,985	5,068	3,964
Net income	$ 934	$ 1,183	$ 1,139	$ 1,551	$ 424	$ 960	$ 1,054	$ 1,312	$ 4,807	$ 3,750	$ 3,843
Basic net income per share	$ 3.69	$ 4.64	$ 4.44	$ 6.03	$ 1.64	$ 3.70	$ 4.07	$ 5.13	$ 18.81	$ 14.53	$ 14.70
Diluted net income per share	$ 3.62	$ 4.55	$ 4.36	$ 5.91	$ 1.61	$ 3.62	$ 3.98	$ 4.99	$ 18.47	$ 14.19	$ 14.35