SCHEDULE I - PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 5,639	$ 5,284	$ 2,173
Cash flows from investing activities:
Acquisitions, net of cash acquired	(709)	0	(354)
Purchase of equity method investment in Kindred at Home	0	0	(1,095)
Purchases of investment securities	(9,125)	(6,361)	(4,687)
Proceeds from sale of investment securities	2,747	4,086	3,494
Maturities of investment securities	4,986	1,733	972
Purchases of property and equipment, net	(964)	(736)	(612)
Net cash used in investing activities	(3,065)	(1,278)	(3,087)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	1,088	987	0
Repayment of senior notes	(400)	(400)	0
Proceeds (repayments) from issuance of commercial paper, net	295		485
Proceeds (repayments) from issuance of commercial paper, net		(360)
Proceeds from term loan	1,000	0	1,000
Repayment of term loan	(1,000)	(650)	(350)
Change in book overdraft	95	54	30
Common stock repurchases	(1,820)	(1,070)	(1,090)
Dividends paid	(323)	(291)	(265)
Proceeds from stock option exercises & other	49	58	45
Net cash used in financing activities	(1,955)	(2,295)	(785)
Increase (decrease) in cash and cash equivalents	619	1,711	(1,699)
Cash and cash equivalents at beginning of period	4,054	2,343	4,042
Cash and cash equivalents at end of period	4,673	4,054	2,343
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	2,531	3,529	2,719
Cash flows from investing activities:
Acquisitions, net of cash acquired	(709)	0	(354)
Purchase of equity method investment in Kindred at Home	0	0	(1,095)
Capital contributions to operating subsidiaries	(538)	(423)	(697)
Purchases of investment securities	(460)	(204)	(145)
Proceeds from sale of investment securities	13	15	35
Maturities of investment securities	411	134	59
Purchases of property and equipment, net	(785)	(585)	(465)
Net cash used in investing activities	(2,068)	(1,063)	(2,662)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	1,088	987	0
Repayment of senior notes	(400)	(400)	0
Proceeds (repayments) from issuance of commercial paper, net	295		485
Proceeds (repayments) from issuance of commercial paper, net		(360)
Proceeds from term loan	1,000	0	1,000
Repayment of term loan	(1,000)	(650)	(350)
Change in book overdraft	80	2	(3)
Common stock repurchases	(1,820)	(1,070)	(1,090)
Dividends paid	(323)	(291)	(265)
Proceeds from stock option exercises & other	47	57	48
Net cash used in financing activities	(1,033)	(1,725)	(175)
Increase (decrease) in cash and cash equivalents	(570)	741	(118)
Cash and cash equivalents at beginning of period	1,006	265	383
Cash and cash equivalents at end of period	$ 436	$ 1,006	$ 265