SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 4,587	$ 2,262	$ 5,639
Net Cash Provided by (Used in) Investing Activities [Abstract]
Acquisitions, net of cash and cash equivalents acquired	(337)	(4,187)	(709)
Purchases of investment securities	(6,049)	(7,197)	(9,125)
Proceeds from sale of investment securities	2,434	3,547	2,747
Maturities of investment securities	1,365	2,597	4,986
Purchases of property and equipment, net	(1,120)	(1,316)	(964)
Net cash used in investing activities	(1,006)	(6,556)	(3,065)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Proceeds from issuance of senior notes, net	1,982	2,984	1,088
Debt issue costs	(6)	(31)	0
Repayment of senior notes	(1,000)	0	(400)
(Repayments) proceeds from issuance of commercial paper, net	(376)	352	295
Proceeds from term loan	0	2,500	1,000
Repayment of term loan	(2,000)	(2,078)	(1,000)
Change in book overdraft	(28)	6	95
Common stock repurchases	(2,096)	(79)	(1,820)
Dividends paid	(392)	(354)	(323)
Net cash (used in) provided by financing activities	(1,914)	3,015	(1,955)
Increase (decrease) in cash and cash equivalents	1,667	(1,279)	619
Cash and cash equivalents at beginning of period	3,394	4,673	4,054
Cash and cash equivalents at end of period	5,061	3,394	4,673
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	4,868	2,853	2,531
Net Cash Provided by (Used in) Investing Activities [Abstract]
Acquisitions, net of cash and cash equivalents acquired	(337)	(4,187)	(709)
Capital contributions to operating subsidiaries	(484)	(2,580)	(538)
Purchases of investment securities	(63)	(200)	(460)
Proceeds from sale of investment securities	468	71	13
Maturities of investment securities	30	122	411
Purchases of property and equipment, net	(931)	(958)	(785)
Net cash used in investing activities	(1,317)	(7,732)	(2,068)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Proceeds from issuance of senior notes, net	1,976	2,953	1,088
Repayment of senior notes	(1,000)	0	(400)
(Repayments) proceeds from issuance of commercial paper, net	(376)	352	295
Proceeds from term loan	0	2,500	1,000
Repayment of term loan	(2,000)	0	(1,000)
Change in book overdraft	5	(52)	80
Common stock repurchases	(2,096)	(79)	(1,820)
Dividends paid	(392)	(354)	(323)
Other, net	40	29	47
Net cash (used in) provided by financing activities	(3,843)	5,349	(1,033)
Increase (decrease) in cash and cash equivalents	(292)	470	(570)
Cash and cash equivalents at beginning of period	906	436	1,006
Cash and cash equivalents at end of period	$ 614	$ 906	$ 436