BUSINESS ACQUISITIONS - Consideration Paid (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Business Acquisition [Line Items]
Goodwill	$ 8,605	$ 7,733
Acquisitions During Period
Business Acquisition [Line Items]
Cash and cash equivalents	50
Accounts receivable	30
Other current assets	25
Property, plant and equipment	259
Finance lease assets (recorded in property, plant and equipment)	17
Operating lease right-of-use assets	84
Goodwill	872
Intangible assets	641
Other assets	36
Total assets acquired	2,014
Accounts payable and accrued expenses	67
Current portion of long-term operating lease liabilities	21
Finance lease liabilities (recorded in long-term debt)	17
Long-term operating lease liabilities	63
Other liabilities	15
Total liabilities assumed	183
Net assets acquired	1,831
LifeLabs Inc.
Business Acquisition [Line Items]
Cash and cash equivalents	50
Accounts receivable	30
Other current assets	23
Property, plant and equipment	255
Finance lease assets (recorded in property, plant and equipment)	0
Operating lease right-of-use assets	67
Goodwill	300
Intangible assets	434
Other assets	36
Total assets acquired	1,195
Accounts payable and accrued expenses	67
Current portion of long-term operating lease liabilities	17
Finance lease liabilities (recorded in long-term debt)	0
Long-term operating lease liabilities	50
Other liabilities	8
Total liabilities assumed	142
Net assets acquired	1,053
Laboratory Business of Three Physician Groups in New York
Business Acquisition [Line Items]
Cash and cash equivalents	0
Accounts receivable	0
Other current assets	0
Property, plant and equipment	0
Finance lease assets (recorded in property, plant and equipment)	0
Operating lease right-of-use assets	0
Goodwill	243
Intangible assets	57
Other assets	0
Total assets acquired	300
Accounts payable and accrued expenses	0
Current portion of long-term operating lease liabilities	0
Finance lease liabilities (recorded in long-term debt)	0
Long-term operating lease liabilities	0
Other liabilities	0
Total liabilities assumed	0
Net assets acquired	300
Select Assets of the Outreach Laboratory Services Business of Allina Health
Business Acquisition [Line Items]
Cash and cash equivalents	0
Accounts receivable	0
Other current assets	0
Property, plant and equipment	0
Finance lease assets (recorded in property, plant and equipment)	0
Operating lease right-of-use assets	0
Goodwill	175
Intangible assets	55
Other assets	0
Total assets acquired	230
Accounts payable and accrued expenses	0
Current portion of long-term operating lease liabilities	0
Finance lease liabilities (recorded in long-term debt)	0
Long-term operating lease liabilities	0
Other liabilities	0
Total liabilities assumed	0
Net assets acquired	230
Other Acquisitions
Business Acquisition [Line Items]
Cash and cash equivalents	0
Accounts receivable	0
Other current assets	2
Property, plant and equipment	4
Finance lease assets (recorded in property, plant and equipment)	17
Operating lease right-of-use assets	17
Goodwill	154
Intangible assets	95
Other assets	0
Total assets acquired	289
Accounts payable and accrued expenses	0
Current portion of long-term operating lease liabilities	4
Finance lease liabilities (recorded in long-term debt)	17
Long-term operating lease liabilities	13
Other liabilities	7
Total liabilities assumed	41
Net assets acquired	$ 248