SCHEDULE I-PARENT COMPANY FINANCIAL INFORMATION (Condensed Statements of Cash Flows) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 2,173	$ 4,051	$ 1,936
Cash flows from investing activities:
Acquisitions, net of cash acquired	(354)	(31)	(7)
Acquisition, equity method investment in Kindred at Home	(1,095)	0	0
Purchases of investment securities	(4,687)	(6,265)	(6,566)
Proceeds from sale of investment securities	3,494	2,768	4,312
Maturities of investment securities	972	1,111	1,426
Purchases of property and equipment, net	(612)	(524)	(527)
Net cash used in investing activities	(3,087)	(2,941)	(1,362)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	0	1,779	0
Proceeds from issuance (repayments) of commercial paper, net	485	(153)	(2)
Proceeds from term loan	1,000	0	0
Repayment of term loan	(350)	0	0
Repayment of long-term debt	0	(800)	0
Change in book overdraft	30	(71)	(89)
Common stock repurchases	(1,090)	(3,365)	(104)
Dividends paid	(265)	(220)	(177)
Proceeds from stock option exercises and other, net	50	63	14
Net cash (used in) provided by financing activities	(785)	(945)	732
(Decrease) increase in cash and cash equivalents	(1,699)	165	1,306
Cash and cash equivalents at beginning of year	4,042	3,877	2,571
Cash and cash equivalents at end of year	2,343	4,042	3,877
Parent Company
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	2,719	2,423	1,848
Cash flows from investing activities:
Acquisitions, net of cash acquired	(354)	0	0
Acquisition, equity method investment in Kindred at Home	(1,095)	0	0
Capital contributions to operating subsidiaries	(697)	(695)	(895)
Purchases of investment securities	(145)	(53)	(151)
Proceeds from sale of investment securities	35	0	25
Maturities of investment securities	59	51	143
Purchases of property and equipment, net	(465)	(359)	(382)
Net cash used in investing activities	(2,662)	(1,056)	(1,260)
Cash flows from financing activities:
Proceeds from issuance of senior notes, net	0	1,779	0
Proceeds from issuance (repayments) of commercial paper, net	485	(153)	(2)
Proceeds from term loan	1,000	0	0
Repayment of term loan	(350)	0	0
Repayment of long-term debt	0	(800)	0
Change in book overdraft	(3)	3	5
Common stock repurchases	(1,090)	(3,365)	(104)
Dividends paid	(265)	(220)	(177)
Proceeds from stock option exercises and other, net	48	62	11
Net cash (used in) provided by financing activities	(175)	(2,694)	(267)
(Decrease) increase in cash and cash equivalents	(118)	(1,327)	321
Cash and cash equivalents at beginning of year	383	1,710	1,389
Cash and cash equivalents at end of year	$ 265	$ 383	$ 1,710