Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Revenue	$ 3,115	$ 3,141	$ 9,555	$ 9,705
Expense:
Compensation and benefits	1,878	1,904	5,434	5,619
Other operating expenses	776	792	2,296	2,321
Operating expenses	2,654	2,696	7,730	7,940
Operating income	461	445	1,825	1,765
Interest income	3	6	9	16
Interest expense	(41)	(45)	(117)	(129)
Investment income (loss)	34	26	39	37
Income before income taxes	457	432	1,756	1,689
Income tax expense	128	127	500	487
Income from continuing operations	329	305	1,256	1,202
Discontinued operations, net of tax	2	(1)	(1)	(4)
Net income before non-controlling interests	331	304	1,255	1,198
Less: Net income attributable to non-controlling interests	8	7	31	27
Net income attributable to the Company	$ 323	$ 297	$ 1,224	$ 1,171
Basic net income per share
Basic net income per share - Continuing operations (usd per share)	$ 0.61	$ 0.55	$ 2.29	$ 2.15
Basic net income per share - Net income attributable to the Company (usd per share)	0.61	0.55	2.29	2.14
Diluted net income per share
Diluted net income per share - Continuing operations (usd per share)	0.60	0.54	2.27	2.12
Diluted net income per share - Net income attributable to the Company (usd per share)	$ 0.61	$ 0.54	$ 2.27	$ 2.11
Average number of shares outstanding
Average number of shares outstanding - Basic	528	544	534	547
Average number of shares outstanding - Diluted	533	551	540	554
Shares outstanding at September 30	522	542	522	542