Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenue	$ 4,349	$ 3,734	$ 8,420	$ 7,734
Expense:
Compensation and benefits	2,537	2,135	4,819	4,359
Other operating expenses	1,132	908	1,983	1,776
Operating expenses	3,669	3,043	6,802	6,135
Operating income	680	691	1,618	1,599
Other net benefit credits	70	65	134	131
Interest income	2	3	30	6
Interest expense	(141)	(68)	(261)	(129)
Cost of extinguishment of debt	(32)	0	(32)	0
Investment income	8	28	13	28
Acquisition related derivative contracts	(37)	0	(8)	0
Income before income taxes	550	719	1,494	1,635
Income tax expense	206	183	423	403
Net income before non-controlling interests	344	536	1,071	1,232
Less: Net income attributable to non-controlling interests	12	5	23	11
Net income attributable to the Company	$ 332	$ 531	$ 1,048	$ 1,221
Net income Per Share Attributable to the Company:
Basic net income per share attributable to the Company (usd per share)	$ 0.66	$ 1.05	$ 2.07	$ 2.41
Diluted net income per share attributable to the Company (usd per share)	$ 0.65	$ 1.04	$ 2.05	$ 2.38
Average number of shares outstanding:
Average number of shares outstanding - Basic (in shares)	507	507	506	507
Average number of shares outstanding - Diluted (in shares)	512	512	511	513
Shares outstanding (in shares)	507	505	507	505