POLICY LIABILITIES - Changes in Liability for Unpaid Policy Claims (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Liability for Unpaid Claims and Claims Expenses
Net balance, beginning of period	$ 5,187
Less claims paid during the period on claims incurred during:
Net balance, end of period	4,948
Total liability for unpaid policy claims	4,948	$ 4,693
Health insurance
Liability for Unpaid Claims and Claims Expenses
Unpaid supplemental health claims, beginning of period	4,389	3,968
Less reinsurance recoverables	39	31
Net balance, beginning of period	4,350	3,937
Add claims incurred during the period related to:
Current year	1,859	1,837
Prior years	(320)	(136)
Total incurred	1,539	1,701
Less claims paid during the period on claims incurred during:
Current year	511	556
Prior years	1,061	1,144
Total paid	1,572	1,700
Effect of foreign exchange rate changes on unpaid claims	(162)	12
Net balance, end of period	4,155	3,950
Add reinsurance recoverables	37	33
Total liability for unpaid policy claims	4,192	3,983
Life insurance
Less claims paid during the period on claims incurred during:
Total liability for unpaid policy claims	$ 756	$ 710