POLICY LIABILITIES - Changes in Liability for Unpaid Policy Claims (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Liability for Unpaid Claims and Claims Expenses
Net balance, beginning of period			$ 4,584
Less claims paid during the period on claims incurred during:
Net balance, end of period	$ 4,741		4,741
Total liability for unpaid policy claims	4,741	$ 4,530	4,741	$ 4,530
Health insurance
Liability for Unpaid Claims and Claims Expenses
Unpaid supplemental health claims, beginning of period	4,024	3,942	3,952	3,881
Less reinsurance recoverables	31	29	28	28
Net balance, beginning of period	3,993	3,913	3,924	3,853
Add claims incurred during the period related to:
Current year	1,806	1,760	5,415	5,381
Prior years	(134)	(131)	(437)	(456)
Total incurred	1,672	1,629	4,978	4,925
Less claims paid during the period on claims incurred during:
Current year	1,421	1,357	3,150	3,109
Prior years	220	217	1,794	1,751
Total paid	1,641	1,574	4,944	4,860
Effect of foreign exchange rate changes on unpaid claims	(3)	(59)	63	(9)
Net balance, end of period	4,021	3,909	4,021	3,909
Add reinsurance recoverables	31	29	31	29
Total liability for unpaid policy claims	4,052	3,938	4,052	3,938
Life insurance
Less claims paid during the period on claims incurred during:
Total liability for unpaid policy claims	$ 689	$ 592	$ 689	$ 592