GUARANTEES, LEASES AND COMMITMENTS - Guarantees (Details)	Mar. 31, 2020 USD ($) trust	Dec. 31, 2019 USD ($) trust
Maximum potential amount of future payments
Expire within 1 year	$ 250,300,000,000	$ 253,600,000,000
Expire after 1 year	144,800,000,000	164,000,000,000.0
Total amount outstanding	395,100,000,000	417,600,000,000
Carrying value	$ 2,884,000,000	$ 706,000,000
Number of trusts funded by the reinsurer | trust	2	2
Fair value of securities in trusts funded by reinsurer relating to indemnification	$ 8,600,000,000	$ 8,600,000,000
Liability related to long-term care insurance indemnification	0	0
Cash collateral available to reimburse losses realized under guarantees and indemnifications	46,200,000,000	46,700,000,000
Securities and other marketable assets held as collateral	80,100,000,000	58,600,000,000
Letters of credit in favor of the Company held as collateral	3,600,000,000	4,400,000,000
Financial standby letters of credit
Maximum potential amount of future payments
Expire within 1 year	29,300,000,000	31,900,000,000
Expire after 1 year	57,300,000,000	62,400,000,000
Total amount outstanding	86,600,000,000	94,300,000,000
Carrying value	147,000,000	140,000,000
Performance guarantees
Maximum potential amount of future payments
Expire within 1 year	6,500,000,000	6,900,000,000
Expire after 1 year	5,600,000,000	5,500,000,000
Total amount outstanding	12,100,000,000	12,400,000,000
Carrying value	23,000,000	21,000,000
Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Expire within 1 year	22,300,000,000	35,200,000,000
Expire after 1 year	51,700,000,000	60,800,000,000
Total amount outstanding	74,000,000,000.0	96,000,000,000.0
Carrying value	2,660,000,000	474,000,000
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	7,000,000	7,000,000
Repurchase reserve for Consumer mortgages representations and warranties	32,000,000	37,000,000
Securities lending indemnifications
Maximum potential amount of future payments
Expire within 1 year	107,800,000,000	87,800,000,000
Expire after 1 year	0	0
Total amount outstanding	107,800,000,000	87,800,000,000
Carrying value	0	0
Credit card merchant processing
Maximum potential amount of future payments
Expire within 1 year	84,200,000,000	91,600,000,000
Expire after 1 year	0	0
Total amount outstanding	84,200,000,000	91,600,000,000
Carrying value	0	0
Credit card arrangements with partners
Maximum potential amount of future payments
Expire within 1 year	200,000,000	200,000,000
Expire after 1 year	400,000,000	400,000,000
Total amount outstanding	600,000,000	600,000,000
Carrying value	7,000,000	23,000,000
Custody indemnifications and other
Maximum potential amount of future payments
Expire within 1 year	0	0
Expire after 1 year	28,600,000,000	33,700,000,000
Total amount outstanding	28,600,000,000	33,700,000,000
Carrying value	40,000,000	41,000,000
Futures and over-the-counter derivatives clearing
Maximum potential amount of future payments
Amount of cash initial margin collected and remitted	$ 18,100,000,000	$ 13,300,000,000