Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Revenue	$ 4,000	$ 3,503
Expense:
Compensation and benefits	2,224	2,005
Other operating expenses	868	749
Operating expenses	3,092	2,754
Operating income	908	749
Other net benefit credits	66	60
Interest income	3	2
Interest expense	(61)	(58)
Investment income	0	0
Income before income taxes	916	753
Income tax expense	220	175
Net income before non-controlling interests	696	578
Less: Net income attributable to non-controlling interests	6	9
Net income attributable to the Company	$ 690	$ 569
Net Income Per Share Attributable to the Company:
Basic net income per share attributable to the Company (usd per share)	$ 1.36	$ 1.10
Diluted net income per share attributable to the Company (usd per share)	$ 1.34	$ 1.09
Average number of shares outstanding:
Average number of shares outstanding - Basic	508	515
Average number of shares outstanding - Diluted	514	522
Shares outstanding at March 31,	508	515