Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Revenue	$ 3,376	$ 3,225	$ 6,712	$ 6,440
Expense:
Compensation and benefits	1,872	1,826	3,726	3,556
Other operating expenses	778	770	1,527	1,520
Operating expenses	2,650	2,596	5,253	5,076
Operating income	726	629	1,459	1,364
Interest income	2	3	4	6
Interest expense	(48)	(40)	(94)	(76)
Investment income (loss)	1	3	(2)	5
Income before income taxes	681	595	1,367	1,299
Income tax expense	201	166	397	372
Income from continuing operations	480	429	970	927
Discontinued operations, net of tax	0	0	0	(3)
Net income before non-controlling interests	480	429	970	924
Less: Net income attributable to non-controlling interests	8	10	17	23
Net income attributable to the Company	$ 472	$ 419	$ 953	$ 901
Basic net income per share
Basic net income per share - Continuing operations (usd per share)	$ 0.91	$ 0.78	$ 1.83	$ 1.68
Basic net income per share - Net income attributable to the Company (usd per share)	0.91	0.78	1.83	1.68
Diluted net income per share
Diluted net income per share - Continuing operations (usd per share)	0.90	0.77	1.81	1.66
Diluted net income per share - Net income attributable to the Company (usd per share)	$ 0.90	$ 0.77	$ 1.81	$ 1.66
Average number of shares outstanding
Average number of shares outstanding - Basic	521	535	521	537
Average number of shares outstanding - Diluted	525	541	526	543
Shares outstanding at June 30,	519	531	519	531