Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue	$ 4,264	$ 3,712	$ 16,652	$ 14,950	$ 14,024
Expense:
Compensation and benefits			9,734	8,605	8,085
Other operating expenses			4,241	3,584	3,284
Operating expenses			13,975	12,189	11,369
Operating income	592	621	2,677	2,761	2,655
Other net benefits credits			265	215	201
Interest income			39	11	9
Interest expense			(524)	(290)	(237)
Cost of extinguishment of debt			(32)	0	0
Investment income (loss)			22	(12)	15
Acquisition related derivative contracts			(8)	(441)	0
Income before income taxes			2,439	2,244	2,643
Income tax expense			666	574	1,133
Income from continuing operations	396	159	1,773	1,670	1,510
Discontinued operations, net of tax			0	0	2
Net income before non-controlling interests			1,773	1,670	1,512
Less: Net income attributable to non-controlling interests			31	20	20
Net income attributable to the Company	$ 391	$ 153	$ 1,742	$ 1,650	$ 1,492
Basic net income per share
Continuing operations (in dollars per share)			$ 3.44	$ 3.26	$ 2.91
Net income attributable to the Company (in dollars per share)	$ 0.77	$ 0.30	3.44	3.26	2.91
Diluted net income per share
Continuing operations (in dollars per share)			3.41	3.23	2.87
Net income attributable to the Company (in dollars per share)	$ 0.76	$ 0.30	$ 3.41	$ 3.23	$ 2.87
Average number of shares outstanding
Basic (in shares)			506	506	513
Diluted (in shares)			511	511	519
Shares outstanding (in shares)	504	504	504	504	509