PLEDGED ASSETS, COLLATERAL, GUARANTEES AND COMMITMENTS - Guarantees (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) margin	Dec. 31, 2018 USD ($)	Dec. 31, 2000 trust
Maximum potential amount of future payments
Expire Within One Year	$ 255,900,000,000	$ 256,600,000,000
Expire After One Year	163,300,000,000	196,500,000,000
Total amount outstanding	419,200,000,000	453,100,000,000
Carrying value	521,000,000	939,000,000
Compensation for standard representations and warranties	0
Stated or notional amounts included in the indemnification clauses	0
Number of trusts funded by the reinsurer | trust			2
Fair value of securities in trusts funded by reinsurer relating to indemnification	8,600,000,000	7,500,000,000
Liability related to long-term care insurance indemnification	0	0
Amount of cash initial margin collected and remitted	13,300,000,000	13,800,000,000
Cash collateral available to reimburse losses realized under guarantees and indemnifications	46,700,000,000	38,000,000,000.0
Available-for-sale securities, pledged to creditors	45,800,000,000	54,700,000,000
Letters of credit in favor of the Company held as collateral	4,400,000,000	4,100,000,000
Financial standby letters of credit
Maximum potential amount of future payments
Expire Within One Year	31,900,000,000	32,100,000,000
Expire After One Year	62,400,000,000	67,500,000,000
Total amount outstanding	94,300,000,000	99,600,000,000
Carrying value	140,000,000	131,000,000
Performance guarantees
Maximum potential amount of future payments
Expire Within One Year	6,900,000,000	7,700,000,000
Expire After One Year	5,500,000,000	4,200,000,000
Total amount outstanding	12,400,000,000	11,900,000,000
Carrying value	21,000,000	29,000,000
Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Expire Within One Year	37,500,000,000	23,500,000,000
Expire After One Year	60,100,000,000	87,400,000,000
Total amount outstanding	97,600,000,000	110,900,000,000
Carrying value	289,000,000	567,000,000
Loans sold with recourse
Maximum potential amount of future payments
Expire Within One Year	0	0
Expire After One 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	9,000,000
Repurchase reserve for Consumer mortgages representations and warranties	37,000,000	49,000,000
Securities lending indemnifications
Maximum potential amount of future payments
Expire Within One Year	87,800,000,000	98,300,000,000
Expire After One Year	0	0
Total amount outstanding	87,800,000,000	98,300,000,000
Carrying value	0	0
Credit card merchant processing
Maximum potential amount of future payments
Expire Within One Year	91,600,000,000	94,700,000,000
Expire After One Year	0	0
Total amount outstanding	91,600,000,000	94,700,000,000
Carrying value	0	0
Credit card arrangements with partners
Maximum potential amount of future payments
Expire Within One Year	200,000,000	300,000,000
Expire After One Year	400,000,000	800,000,000
Total amount outstanding	600,000,000	1,100,000,000
Carrying value	23,000,000	162,000,000
Custody indemnifications and other
Maximum potential amount of future payments
Expire Within One Year	0	0
Expire After One Year	33,700,000,000	35,400,000,000
Total amount outstanding	33,700,000,000	35,400,000,000
Carrying value	$ 41,000,000	41,000,000
Futures and over the counter derivatives clearing
Maximum potential amount of future payments
Number of types of margin | margin	2
Investment Grade
Maximum potential amount of future payments
Total amount outstanding	$ 97,400,000,000	102,700,000,000
Investment Grade | Financial standby letters of credit
Maximum potential amount of future payments
Total amount outstanding	66,400,000,000	71,300,000,000
Investment Grade | Performance guarantees
Maximum potential amount of future payments
Total amount outstanding	9,700,000,000	9,200,000,000
Investment Grade | Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Total amount outstanding	0	0
Investment Grade | Loans sold with recourse
Maximum potential amount of future payments
Total amount outstanding	0	0
Investment Grade | Securities lending indemnifications
Maximum potential amount of future payments
Total amount outstanding	0	0
Investment Grade | Credit card merchant processing
Maximum potential amount of future payments
Total amount outstanding	0	0
Investment Grade | Credit card arrangements with partners
Maximum potential amount of future payments
Total amount outstanding	0	0
Investment Grade | Custody indemnifications and other
Maximum potential amount of future payments
Total amount outstanding	21,300,000,000	22,200,000,000
Non-Investment Grade
Maximum potential amount of future payments
Total amount outstanding	27,200,000,000	27,200,000,000
Non-Investment Grade | Financial standby letters of credit
Maximum potential amount of future payments
Total amount outstanding	12,500,000,000	11,900,000,000
Non-Investment Grade | Performance guarantees
Maximum potential amount of future payments
Total amount outstanding	2,300,000,000	2,100,000,000
Non-Investment Grade | Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Total amount outstanding	0	0
Non-Investment Grade | Loans sold with recourse
Maximum potential amount of future payments
Total amount outstanding	0	0
Non-Investment Grade | Securities lending indemnifications
Maximum potential amount of future payments
Total amount outstanding	0	0
Non-Investment Grade | Credit card merchant processing
Maximum potential amount of future payments
Total amount outstanding	0	0
Non-Investment Grade | Credit card arrangements with partners
Maximum potential amount of future payments
Total amount outstanding	0	0
Non-Investment Grade | Custody indemnifications and other
Maximum potential amount of future payments
Total amount outstanding	12,400,000,000	13,200,000,000
Not Rated
Maximum potential amount of future payments
Total amount outstanding	294,600,000,000	323,200,000,000
Not Rated | Financial standby letters of credit
Maximum potential amount of future payments
Total amount outstanding	15,400,000,000	16,400,000,000
Not Rated | Performance guarantees
Maximum potential amount of future payments
Total amount outstanding	400,000,000	600,000,000
Not Rated | Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Total amount outstanding	97,600,000,000	110,900,000,000
Not Rated | Loans sold with recourse
Maximum potential amount of future payments
Total amount outstanding	1,200,000,000	1,200,000,000
Not Rated | Securities lending indemnifications
Maximum potential amount of future payments
Total amount outstanding	87,800,000,000	98,300,000,000
Not Rated | Credit card merchant processing
Maximum potential amount of future payments
Total amount outstanding	91,600,000,000	94,700,000,000
Not Rated | Credit card arrangements with partners
Maximum potential amount of future payments
Total amount outstanding	600,000,000	1,100,000,000
Not Rated | Custody indemnifications and other
Maximum potential amount of future payments
Total amount outstanding	$ 0	$ 0