POLICY LIABILITIES - Changes in Liability for Unpaid Policy Claims (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Liability for Unpaid Claims and Claims Expenses
Net balance, beginning of period			$ 4,392
Less claims paid during the period on claims incurred during:
Net balance, end of period	$ 4,530		4,530
Total liability for unpaid policy claims	4,530	$ 4,368	4,530	$ 4,368
Health insurance
Liability for Unpaid Claims and Claims Expenses
Unpaid supplemental health claims, beginning of period	3,942	3,872	3,881	3,707
Less reinsurance recoverables	29	30	28	27
Net balance, beginning of period	3,913	3,842	3,853	3,680
Add claims incurred during the period related to:
Current year	1,760	1,759	5,381	5,278
Prior years	(131)	(126)	(456)	(386)
Total incurred	1,629	1,633	4,925	4,892
Less claims paid during the period on claims incurred during:
Current year	1,357	1,357	3,109	3,074
Prior years	217	234	1,751	1,697
Total paid	1,574	1,591	4,860	4,771
Effect of foreign exchange rate changes on unpaid claims	(59)	(14)	(9)	69
Net balance, end of period	3,909	3,870	3,909	3,870
Add reinsurance recoverables	29	30	29	30
Total liability for unpaid policy claims	3,938	3,900	3,938	3,900
Life insurance
Less claims paid during the period on claims incurred during:
Total liability for unpaid policy claims	$ 592	$ 468	$ 592	$ 468