Selected Quarterly Financial Data and Supplemental Information (Unaudited) (Details) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares	Sep. 30, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Sep. 30, 2018 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Feb. 18, 2020 stockholder
Quarterly Financial Data [Abstract]
Revenue	$ 4,264	$ 3,968	$ 4,349	$ 4,071	$ 3,712	$ 3,504	$ 3,734	$ 4,000	$ 16,652	$ 14,950	$ 14,024
Operating income	592	467	680	938	621	541	691	908	2,677	2,761	2,655
Net income before non-controlling interests	396	306	344	727	159	279	536	696	1,773	1,670	1,510
Net income attributable to the Company	$ 391	$ 303	$ 332	$ 716	$ 153	$ 276	$ 531	$ 690	$ 1,742	$ 1,650	$ 1,492
Basic Per Share Data:
Net income attributable to the Company (in dollars per share) | $ / shares	$ 0.77	$ 0.60	$ 0.66	$ 1.42	$ 0.30	$ 0.55	$ 1.05	$ 1.36	$ 3.44	$ 3.26	$ 2.91
Diluted Per Share Data:
Net income attributable to the Company (in dollars per share) | $ / shares	0.76	0.59	0.65	1.40	0.30	0.54	1.04	1.34	$ 3.41	$ 3.23	$ 2.87
Dividends Paid Per Share (in dollars per share) | $ / shares	$ 0.455	$ 0.455	$ 0.415	$ 0.415	$ 0.415	$ 0.415	$ 0.375	$ 0.375
Subsequent Event
Subsequent Event [Line Items]
Number of stockholders of record | stockholder												4,875