Consolidated Statements of Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenue	$ 3,503	$ 3,336
Expense:
Compensation and benefits	1,945	1,854
Other operating expenses	749	749
Operating expenses	2,694	2,603
Operating income	809	733
Interest income	2	2
Interest expense	(58)	(46)
Investment income (loss)	1	(3)
Income before income taxes	753	686
Income tax expense	175	196
Net income before non-controlling interests	578	490
Less: Net income attributable to non-controlling interests	9	9
Net income attributable to the Company	$ 569	$ 481
Net Income Per Share Attributable to the Company:
Basic net income per share attributable to the Company (usd per share)	$ 1.10	$ 0.92
Diluted net income per share attributable to the Company (usd per share)	$ 1.09	$ 0.91
Average number of shares outstanding:
Average number of shares outstanding - Basic	515	521
Average number of shares outstanding - Diluted	522	526
Shares outstanding at March 31,	515	521