SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 3,981	$ 4,587	$ 2,262
Net Cash Provided by (Used in) Investing Activities [Abstract]
Acquisitions, net of cash and cash equivalents acquired	(233)	(337)	(4,187)
Purchases of property and equipment, net	(1,004)	(1,137)	(1,342)
Purchases of investment securities	(7,552)	(6,049)	(7,197)
Proceeds from sale of investment securities	3,795	2,434	3,547
Maturities of investment securities	1,292	1,365	2,597
Net cash used in investing activities	(3,492)	(1,006)	(6,556)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	2,544	1,982	2,984
Repayment of senior notes	(1,832)	(1,000)	0
Proceeds (repayments) from issuance of commercial paper, net	211	(376)	352
Change in book overdraft	55	(28)	6
Common stock repurchases	(1,573)	(2,096)	(79)
Dividends paid	(431)	(392)	(354)
Net cash (used in) provided by financing activities	(856)	(1,914)	3,015
(Decrease) increase in cash and cash equivalents	(367)	1,667	(1,279)
Cash and cash equivalents at beginning of period	5,061	3,394	4,673
Cash and cash equivalents at end of period	4,694	5,061	3,394
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	3,042	4,868	2,853
Net Cash Provided by (Used in) Investing Activities [Abstract]
Acquisitions, net of cash and cash equivalents acquired	(233)	(337)	(4,187)
Capital contributions to operating subsidiaries	(792)	(484)	(2,580)
Purchases of property and equipment, net	(761)	(931)	(958)
Purchases of investment securities	(17)	(63)	(200)
Proceeds from sale of investment securities	41	468	71
Maturities of investment securities	67	30	122
Net cash used in investing activities	(1,695)	(1,317)	(7,732)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	2,537	1,976	2,953
Repayment of senior notes	(1,832)	(1,000)	0
Proceeds (repayments) from issuance of commercial paper, net	211	(376)	352
Proceeds from term loan	0	0	2,500
Repayment of term loan	(500)	(2,000)	0
Change in book overdraft	2	5	(52)
Common stock repurchases	(1,573)	(2,096)	(79)
Dividends paid	(431)	(392)	(354)
Other, net	(125)	40	29
Net cash (used in) provided by financing activities	(1,711)	(3,843)	5,349
(Decrease) increase in cash and cash equivalents	(364)	(292)	470
Cash and cash equivalents at beginning of period	614	906	436
Cash and cash equivalents at end of period	$ 250	$ 614	$ 906