Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenue	$ 4,071	$ 4,000
Expense:
Compensation and benefits	2,282	2,224
Other operating expenses	851	868
Operating expenses	3,133	3,092
Operating income	938	908
Other net benefit credits	64	66
Interest income	28	3
Interest expense	(120)	(61)
Investment income	5	0
Change in fair value of acquisition related derivative contracts	29	0
Income before income taxes	944	916
Income tax expense	217	220
Net income before non-controlling interests	727	696
Less: Net income attributable to non-controlling interests	11	6
Net income attributable to the Company	$ 716	$ 690
Net income Per Share Attributable to the Company:
Basic net income per share attributable to the Company (usd per share)	$ 1.42	$ 1.36
Diluted net income per share attributable to the Company (usd per share)	$ 1.40	$ 1.34
Average number of shares outstanding:
Average number of shares outstanding - Basic (in shares)	505	508
Average number of shares outstanding - Diluted (in shares)	511	514
Shares outstanding at March 31,	507	508