Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Revenue	$ 3,135	$ 3,115	$ 9,847	$ 9,555
Expense:
Compensation and benefits	1,817	1,878	5,543	5,434
Other operating expenses	746	776	2,273	2,296
Operating expenses	2,563	2,654	7,816	7,730
Operating income	572	461	2,031	1,825
Interest income	0	3	4	9
Interest expense	(47)	(41)	(141)	(117)
Investment income (loss)	1	34	(2)	39
Income before income taxes	525	457	1,892	1,756
Income tax expense	141	128	538	500
Income from continuing operations	384	329	1,354	1,256
Discontinued operations, net of tax	0	2	0	(1)
Net income before non-controlling interests	384	331	1,354	1,255
Less: Net income attributable to non-controlling interests	5	8	22	31
Net income attributable to the Company	$ 379	$ 323	$ 1,332	$ 1,224
Basic net income per share
Basic net income per share - Continuing operations (usd per share)	$ 0.73	$ 0.61	$ 2.56	$ 2.29
Basic net income per share - Net income attributable to the Company (usd per share)	0.73	0.61	2.56	2.29
Diluted net income per share
Diluted net income per share - Continuing operations (usd per share)	0.73	0.60	2.54	2.27
Diluted net income per share - Net income attributable to the Company (usd per share)	$ 0.73	$ 0.61	$ 2.54	$ 2.27
Average number of shares outstanding
Average number of shares outstanding - Basic	518	528	520	534
Average number of shares outstanding - Diluted	523	533	525	540
Shares outstanding at September 30,	516	522	516	522