Acquisition and Divestiture - Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Nov. 28, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill	$ 79,548	$ 78,678
Aetna Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [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			47,554
Intangible assets			22,571
Other long-term assets			8,249
Total assets acquired			110,911
Health care costs payable			5,302
Other current liabilities			10,069
Debt (current and long-term)			8,098
Deferred income taxes			4,278
Deferred income taxes			13,078
Total liabilities assumed			40,825
Noncontrolling interests			320
Total consideration transferred			$ 69,766