Acquisitions and Divestitures - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Nov. 28, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 79,749	$ 78,678		$ 38,451
Aetna Inc.
Business Acquisition [Line Items]
Cash and cash equivalents			$ 6,565
Accounts receivable			4,094
Other current assets			3,894
Investments (current and long-term)			17,984
Goodwill			47,755
Intangible assets			22,571
Other assets			8,249
Total assets acquired			111,112
Health care costs payable			5,302
Other current liabilities			9,940
Debt (current and long-term)			8,098
Deferred income taxes			4,608
Other long-term liabilities			13,078
Total liabilities assumed			41,026
Noncontrolling interests			320
Total consideration transferred			$ 69,766