GUARANTEES, LEASES AND COMMITMENTS - Guarantees (Details)	Jun. 30, 2019 USD ($) trust	Dec. 31, 2018 USD ($) trust
Maximum potential amount of future payments
Expire within 1 year	$ 275,300,000,000	$ 256,600,000,000
Expire after 1 year	167,900,000,000	196,500,000,000
Total amount outstanding	443,200,000,000	453,100,000,000
Carrying value	$ 757,000,000	$ 939,000,000
Number of trusts funded by the reinsurer | trust	2	2
Fair value of securities in trusts funded by reinsurer relating to indemnification	$ 8,300,000,000	$ 7,500,000,000
Liability related to long-term care insurance indemnification	0	0
Cash collateral available to reimburse losses realized under guarantees and indemnifications	71,000,000,000	55,000,000,000
Securities and other marketable assets held as collateral	55,000,000,000	55,000,000,000
Letters of credit in favor of the Company held as collateral	4,000,000,000.0	4,100,000,000
Financial standby letters of credit
Maximum potential amount of future payments
Expire within 1 year	32,900,000,000	32,100,000,000
Expire after 1 year	66,200,000,000	67,500,000,000
Total amount outstanding	99,100,000,000	99,600,000,000
Carrying value	132,000,000	131,000,000
Performance guarantees
Maximum potential amount of future payments
Expire within 1 year	7,700,000,000	7,700,000,000
Expire after 1 year	4,300,000,000	4,200,000,000
Total amount outstanding	12,000,000,000.0	11,900,000,000
Carrying value	27,000,000	29,000,000
Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Expire within 1 year	39,300,000,000	23,500,000,000
Expire after 1 year	63,600,000,000	87,400,000,000
Total amount outstanding	102,900,000,000	110,900,000,000
Carrying value	413,000,000	567,000,000
Loans sold with recourse
Maximum potential amount of future payments
Expire within 1 year	0	0
Expire after 1 year	1,300,000,000	1,200,000,000
Total amount outstanding	1,300,000,000	1,200,000,000
Carrying value	8,000,000	9,000,000
Repurchase reserve for Consumer mortgages representations and warranties	43,000,000	49,000,000
Securities lending indemnifications
Maximum potential amount of future payments
Expire within 1 year	105,300,000,000	98,300,000,000
Expire after 1 year	0	0
Total amount outstanding	105,300,000,000	98,300,000,000
Carrying value	0	0
Credit card merchant processing
Maximum potential amount of future payments
Expire within 1 year	90,000,000,000.0	94,700,000,000
Expire after 1 year	0	0
Total amount outstanding	90,000,000,000.0	94,700,000,000
Carrying value	0	0
Credit card arrangements with partners
Maximum potential amount of future payments
Expire within 1 year	100,000,000	300,000,000
Expire after 1 year	800,000,000	800,000,000
Total amount outstanding	900,000,000	1,100,000,000
Carrying value	136,000,000	162,000,000
Custody indemnifications and other
Maximum potential amount of future payments
Expire within 1 year	0	0
Expire after 1 year	31,700,000,000	35,400,000,000
Total amount outstanding	31,700,000,000	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
Amount of cash initial margin collected and remitted	$ 14,100,000,000	$ 13,800,000,000