Goodwill and Other Intangibles - Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Intangible Assets[Line Items]
Indefinite-lived intangible assets, Trademarks	$ 10,498	$ 10,498
Finite-lived intangible assets, accumulated amortization	(10,481)	(9,038)
Intangible assets, gross	41,623	42,159
Intangible assets, net	$ 31,142	$ 33,121
Weighted Average Life (years)	15 years 2 months 12 days	15 years 1 month 6 days
Amortization of intangible assets	$ 2,341	$ 2,436	$ 1,006
Customer contracts/relationships and covenants not to compete
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	24,952	25,447
Finite-lived intangible assets, accumulated amortization	(8,923)	(8,128)
Finite-lived intangible assets, net carrying amount	$ 16,029	$ 17,319
Weighted Average Life (years)	14 years 10 months 24 days	14 years 9 months 18 days
Technology
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 1,060	$ 1,060
Finite-lived intangible assets, accumulated amortization	(739)	(386)
Finite-lived intangible assets, net carrying amount	$ 321	$ 674
Weighted Average Life (years)	3 years	3 years
Provider networks
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 4,203	$ 4,200
Finite-lived intangible assets, accumulated amortization	(440)	(229)
Finite-lived intangible assets, net carrying amount	$ 3,763	$ 3,971
Weighted Average Life (years)	20 years	20 years
Value of Business Acquired
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 590	$ 590
Finite-lived intangible assets, accumulated amortization	(119)	(63)
Finite-lived intangible assets, net carrying amount	$ 471	$ 527
Weighted Average Life (years)	20 years	20 years
Other
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 320	$ 364
Finite-lived intangible assets, accumulated amortization	(260)	(232)
Finite-lived intangible assets, net carrying amount	$ 60	$ 132
Weighted Average Life (years)	7 years 8 months 12 days	8 years 1 month 6 days