POLICY LIABILITIES - Changes in Liability for Unpaid Policy Claims (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	$ 4,706		4,706
Total liability for unpaid policy claims	4,706	$ 4,524	4,706	$ 4,524
Health insurance
Liability for Unpaid Claims and Claims Expenses
Unpaid supplemental health claims, beginning of period	3,967	4,041	3,952	3,881
Less reinsurance recoverables	29	31	28	28
Net balance, beginning of period	3,938	4,010	3,924	3,853
Add claims incurred during the period related to:
Current year	1,785	1,779	3,610	3,621
Prior years	(136)	(133)	(303)	(325)
Total incurred	1,649	1,646	3,307	3,296
Less claims paid during the period on claims incurred during:
Current year	1,229	1,226	1,735	1,746
Prior years	430	426	1,568	1,540
Total paid	1,659	1,652	3,303	3,286
Effect of foreign exchange rate changes on unpaid claims	65	(91)	65	50
Net balance, end of period	3,993	3,913	3,993	3,913
Add reinsurance recoverables	31	29	31	29
Total liability for unpaid policy claims	4,024	3,942	4,024	3,942
Life insurance
Less claims paid during the period on claims incurred during:
Total liability for unpaid policy claims	$ 682	$ 582	$ 682	$ 582