GUARANTEES, LEASES AND COMMITMENTS - Guarantees (Details)	Mar. 31, 2021 USD ($) trust	Dec. 31, 2020 USD ($)
Maximum potential amount of future payments
Expire within 1 year	$ 270,600,000,000	$ 266,900,000,000
Expire after 1 year	159,300,000,000	174,600,000,000
Total amount outstanding	429,900,000,000	441,500,000,000
Carrying value	$ 1,695,000,000	2,204,000,000
Number of trusts funded by the reinsurer | trust	2
Liability related to long-term care insurance indemnification	$ 0	0
Amount of cash initial margin collected and remitted	16,800,000,000	16,600,000,000
Cash collateral available to reimburse losses realized under guarantees and indemnifications	60,500,000,000	51,600,000,000
Securities and other marketable assets held as collateral	92,200,000,000	80,100,000,000
Letters of credit in favor of the Company held as collateral	4,900,000,000	6,600,000,000
Financial standby letters of credit
Maximum potential amount of future payments
Expire within 1 year	23,300,000,000	25,300,000,000
Expire after 1 year	70,800,000,000	68,400,000,000
Total amount outstanding	94,100,000,000	93,700,000,000
Carrying value	1,123,000,000	1,407,000,000
Performance guarantees
Maximum potential amount of future payments
Expire within 1 year	6,600,000,000	7,300,000,000
Expire after 1 year	6,200,000,000	6,000,000,000.0
Total amount outstanding	12,800,000,000	13,300,000,000
Carrying value	63,000,000	72,000,000
Derivative instruments considered to be guarantees
Maximum potential amount of future payments
Expire within 1 year	12,200,000,000	20,000,000,000.0
Expire after 1 year	57,200,000,000	60,900,000,000
Total amount outstanding	69,400,000,000	80,900,000,000
Carrying value	458,000,000	671,000,000
Loans sold with recourse
Maximum potential amount of future payments
Expire within 1 year	0	0
Expire after 1 year	1,200,000,000	1,200,000,000
Total amount outstanding	1,200,000,000	1,200,000,000
Carrying value	8,000,000	9,000,000
Repurchase reserve for consumer mortgages representations and warranties	32,000,000	31,000,000
Securities lending indemnifications
Maximum potential amount of future payments
Expire within 1 year	132,100,000,000	112,200,000,000
Expire after 1 year	0	0
Total amount outstanding	132,100,000,000	112,200,000,000
Carrying value	0	0
Credit card merchant processing
Maximum potential amount of future payments
Expire within 1 year	96,400,000,000	101,900,000,000
Expire after 1 year	0	0
Total amount outstanding	96,400,000,000	101,900,000,000
Carrying value	3,000,000	3,000,000
Credit card arrangements with partners
Maximum potential amount of future payments
Expire within 1 year	0	200,000,000
Expire after 1 year	800,000,000	800,000,000
Total amount outstanding	800,000,000	1,000,000,000.0
Carrying value	7,000,000	7,000,000
Custody indemnifications and other
Maximum potential amount of future payments
Expire within 1 year	0	0
Expire after 1 year	23,100,000,000	37,300,000,000
Total amount outstanding	23,100,000,000	37,300,000,000
Carrying value	$ 33,000,000	$ 35,000,000