ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Changes in AOCI by Component (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 13,625	$ 11,274	$ 11,274
Other comprehensive income (loss) on investments in net expected credit losses	5	(7)
Ending balance	11,940	9,549	13,625
Total Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	3,548	1,413	1,413
Other comprehensive income (loss) before reclassifications	(1,765)		2,046
Other comprehensive income (loss) on investments in net expected credit losses			24
Other comprehensive income (loss) on investments in net expected credit losses	5
Amounts reclassified from accumulated other comprehensive income (loss)	(27)		65
Ending balance	1,761	(65)	3,548
Unrealized Gains and Losses on Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	3,556	1,421	1,421
Other comprehensive income (loss) before reclassifications	(1,767)		2,048
Other comprehensive income (loss) on investments in net expected credit losses			24
Other comprehensive income (loss) on investments in net expected credit losses	5
Amounts reclassified from accumulated other comprehensive income (loss)	(27)		63
Ending balance	1,767		3,556
Offset of net unrealized losses in AOCI due to impact those net unrealized losses would have on certain of the Company's insurance assets and liabilities had the net unrealized losses been recognized in net income	(1,000)		(2,000)
Accumulated Gain and Loss Derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(8)	$ (8)	(8)
Other comprehensive income (loss) before reclassifications	2		(2)
Other comprehensive income (loss) on investments in net expected credit losses			0
Other comprehensive income (loss) on investments in net expected credit losses	0
Amounts reclassified from accumulated other comprehensive income (loss)	0		2
Ending balance	$ (6)		$ (8)