Goodwill and Other Intangibles - Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
Other Intangible Assets[Line Items]
Indefinite-lived intangible assets, Trademarks	$ 10,498	$ 10,498
Finite-lived intangible assets, accumulated amortization	(9,038)	(7,214)
Intangible assets, gross	42,159	43,738
Intangible assets, net	$ 33,121	$ 36,524	$ 36,307
Weighted Average Life (years)	15 years 1 month 6 days	15 years 3 months 18 days
Customer contracts/relationships and covenants not to compete
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 25,447	$ 26,213
Finite-lived intangible assets, accumulated amortization	(8,128)	(6,349)
Finite-lived intangible assets, net carrying amount	$ 17,319	$ 19,864
Weighted Average Life (years)	14 years 9 months 18 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	(386)	(31)
Finite-lived intangible assets, net carrying amount	$ 674	$ 1,029
Weighted Average Life (years)	3 years	3 years
Provider networks
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 4,200	$ 4,200
Finite-lived intangible assets, accumulated amortization	(229)	(19)
Finite-lived intangible assets, net carrying amount	$ 3,971	$ 4,181
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	(63)	(7)
Finite-lived intangible assets, net carrying amount	$ 527	$ 583
Weighted Average Life (years)	20 years	20 years
Other
Other Intangible Assets[Line Items]
Finite-lived intangible assets, gross carrying amount	$ 364	$ 1,177
Finite-lived intangible assets, accumulated amortization	(232)	(808)
Finite-lived intangible assets, net carrying amount	$ 132	$ 369
Weighted Average Life (years)	8 years 1 month 6 days	17 years 1 month 6 days