Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Revenue	$ 3,968	$ 3,968	$ 12,808	$ 12,388
Expense:
Compensation and benefits	2,495	2,437	7,479	7,256
Other operating expenses	933	1,064	2,834	3,047
Operating expenses	3,428	3,501	10,313	10,303
Operating income	540	467	2,495	2,085
Other net benefit credits	60	69	187	203
Interest income	1	4	5	34
Interest expense	(128)	(133)	(387)	(394)
Cost of extinguishment of debt	0	0	0	(32)
Investment (loss) income	(14)	7	(47)	20
Acquisition related derivative contracts	0	0	0	(8)
Income before income taxes	459	414	2,253	1,908
Income tax expense	139	108	586	531
Net income before non-controlling interests	320	306	1,667	1,377
Less: Net income attributable to non-controlling interests	4	3	25	26
Net income attributable to the Company	$ 316	$ 303	$ 1,642	$ 1,351
Net income per share attributable to the Company:
Basic net income per share attributable to the Company (usd per share)	$ 0.62	$ 0.60	$ 3.25	$ 2.67
Diluted net income per share attributable to the Company (usd per share)	$ 0.62	$ 0.59	$ 3.21	$ 2.64
Average number of shares outstanding:
Average number of shares outstanding - Basic (in shares)	507	506	506	506
Average number of shares outstanding - Diluted (in shares)	512	511	511	511
Shares outstanding (in shares)	507	505	507	505