Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenue	$ 4,651	$ 4,071
Expense:
Compensation and benefits	2,555	2,282
Other operating expenses	1,026	851
Operating expenses	3,581	3,133
Operating income	1,070	938
Other net benefit credits	64	64
Interest income	2	28
Interest expense	(127)	(120)
Investment (loss) income	(2)	5
Acquisition related derivative contracts	0	29
Income before income taxes	1,007	944
Income tax expense	240	217
Net income before non-controlling interests	767	727
Less: Net income attributable to non-controlling interests	13	11
Net income attributable to the Company	$ 754	$ 716
Net income per share attributable to the Company:
Basic net income per share attributable to the Company (usd per share)	$ 1.49	$ 1.42
Diluted net income per share attributable to the Company (usd per share)	$ 1.48	$ 1.40
Average number of shares outstanding:
Average number of shares outstanding - Basic (in shares)	505	505
Average number of shares outstanding - Diluted (in shares)	510	511
Shares outstanding (in shares)	506	507