POLICY LIABILITIES - Changes in Liability for Unpaid Policy Claims (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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	$ 4,524		4,524
Total liability for unpaid policy claims	4,524	$ 4,281	4,524	$ 4,281
Health insurance
Liability for Unpaid Claims and Claims Expenses
Unpaid supplemental health claims, beginning of period	4,041	3,854	3,881	3,707
Less reinsurance recoverables	31	30	28	27
Net balance, beginning of period	4,010	3,824	3,853	3,680
Add claims incurred during the period related to:
Current year	1,779	1,772	3,621	3,520
Prior years	(133)	(138)	(325)	(260)
Total incurred	1,646	1,634	3,296	3,260
Less claims paid during the period on claims incurred during:
Current year	1,226	1,220	1,746	1,721
Prior years	426	400	1,540	1,461
Total paid	1,652	1,620	3,286	3,182
Effect of foreign exchange rate changes on unpaid claims	(91)	4	50	84
Net balance, end of period	3,913	3,842	3,913	3,842
Add reinsurance recoverables	29	30	29	30
Total liability for unpaid policy claims	3,942	3,872	3,942	3,872
Life insurance
Less claims paid during the period on claims incurred during:
Total liability for unpaid policy claims	$ 582	$ 409	$ 582	$ 409