Consolidated Statements Of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue	$ 4,416	$ 4,264	$ 17,224	$ 16,652	$ 14,950
Expense:
Compensation and benefits			10,129	9,734	8,605
Other operating expenses			4,029	4,241	3,584
Operating expenses			14,158	13,975	12,189
Operating income	571	592	3,066	2,677	2,761
Other net benefits credits			257	265	215
Interest income			7	39	11
Interest expense			(515)	(524)	(290)
Cost of extinguishment of debt			0	(32)	0
Investment (loss) income			(22)	22	(12)
Acquisition related derivative contracts			0	(8)	(441)
Income before income taxes			2,793	2,439	2,244
Income tax expense			747	666	574
Net income before non-controlling interests	379	396	2,046	1,773	1,670
Less: Net income attributable to non-controlling interests			30	31	20
Net income attributable to the Company	$ 374	$ 391	$ 2,016	$ 1,742	$ 1,650
Net income per share attributable to the Company
Basic (in dollars per share)	$ 0.74	$ 0.77	$ 3.98	$ 3.44	$ 3.26
Diluted (in dollars per share)	$ 0.73	$ 0.76	$ 3.94	$ 3.41	$ 3.23
Average number of shares outstanding
Basic (in shares)			506	506	506
Diluted (in shares)			512	511	511
Shares outstanding (in shares)	508	504	508	504	504