Acquisitions and Dispositions Disposition (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 6,507	$ 5,920	$ 6,078	$ 5,853	$ 6,047	$ 5,116	$ 4,990	$ 4,765	$ 24,358	$ 20,918	$ 18,274
Current Assets	10,625				9,421				10,625	9,421
Current Liabilities	6,147				$ 7,048				6,147	$ 7,048
Anatomical Pathology business [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues									344
Current Assets	81								81
Long-term Assets	528								528
Current Liabilities	34								34
Long-term Liabilities	$ 24								$ 24
Scenario, Forecast [Member] | Anatomical Pathology business [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Consideration												$ 1,140