GUARANTEES AND COMMITMENTS - Guarantees (Details)	Mar. 31, 2017 USD ($) trust	Dec. 31, 2016 USD ($) trust
Maximum potential amount of future payments
Expire within 1 year	$ 222,800,000,000	$ 207,400,000,000
Expire after 1 year	196,800,000,000	197,800,000,000
Total amount outstanding	419,600,000,000	405,200,000,000
Carrying value	$ 1,190,000,000	$ 1,183,000,000
Number of trusts funded by the reinsurer | trust	2	2
Fair value of securities in trusts funded by reinsurer relating to indemnification	$ 7,100,000,000	$ 7,000,000,000
Liability related to long-term care insurance indemnification	0	0
Cash collateral available to reimburse losses realized under guarantees and indemnifications	55,000,000,000	45,000,000,000
Securities and other marketable assets held as collateral	45,000,000,000	38,000,000,000
Letters of credit in favor of the Company held as collateral	6,000,000,000	5,400,000,000
Investment grade
Maximum potential amount of future payments
Total amount outstanding	120,400,000,000	118,400,000,000
Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	17,500,000,000	17,500,000,000
Not rated
Maximum potential amount of future payments
Total amount outstanding	281,700,000,000	269,300,000,000
Financial standby letters of credit
Maximum potential amount of future payments
Expire within 1 year	28,100,000,000	26,000,000,000
Expire after 1 year	66,000,000,000	67,100,000,000
Total amount outstanding	94,100,000,000	93,100,000,000
Carrying value	205,000,000	141,000,000
Financial standby letters of credit | Investment grade
Maximum potential amount of future payments
Total amount outstanding	65,900,000,000	66,800,000,000
Financial standby letters of credit | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	14,800,000,000	13,400,000,000
Financial standby letters of credit | Not rated
Maximum potential amount of future payments
Total amount outstanding	13,400,000,000	12,900,000,000
Performance guarantees
Maximum potential amount of future payments
Expire within 1 year	7,600,000,000	7,500,000,000
Expire after 1 year	3,700,000,000	3,600,000,000
Total amount outstanding	11,300,000,000	11,100,000,000
Carrying value	20,000,000	19,000,000
Performance guarantees | Investment grade
Maximum potential amount of future payments
Total amount outstanding	7,200,000,000	6,300,000,000
Performance guarantees | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	2,600,000,000	4,000,000,000
Performance guarantees | Not rated
Maximum potential amount of future payments
Total amount outstanding	1,500,000,000	800,000,000
Derivative instruments deemed to be guarantees
Maximum potential amount of future payments
Expire within 1 year	10,700,000,000	7,200,000,000
Expire after 1 year	78,100,000,000	80,000,000,000
Total amount outstanding	88,800,000,000	87,200,000,000
Carrying value	690,000,000	747,000,000
Derivative instruments deemed to be guarantees | Investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Derivative instruments deemed to be guarantees | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Derivative instruments deemed to be guarantees | Not rated
Maximum potential amount of future payments
Total amount outstanding	88,800,000,000	87,200,000,000
Loans sold with recourse
Maximum potential amount of future payments
Expire within 1 year	0	0
Expire after 1 year	200,000,000	200,000,000
Total amount outstanding	200,000,000	200,000,000
Carrying value	11,000,000	12,000,000
Repurchase reserve for Consumer mortgages representations and warranties	104,000,000	107,000,000
Loans sold with recourse | Investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Loans sold with recourse | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Loans sold with recourse | Not rated
Maximum potential amount of future payments
Total amount outstanding	200,000,000	200,000,000
Securities lending indemnifications
Maximum potential amount of future payments
Expire within 1 year	97,100,000,000	80,300,000,000
Expire after 1 year	0	0
Total amount outstanding	97,100,000,000	80,300,000,000
Carrying value	0	0
Securities lending indemnifications | Investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Securities lending indemnifications | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Securities lending indemnifications | Not rated
Maximum potential amount of future payments
Total amount outstanding	97,100,000,000	80,300,000,000
Credit card merchant processing
Maximum potential amount of future payments
Expire within 1 year	77,600,000,000	86,400,000,000
Expire after 1 year	0	0
Total amount outstanding	77,600,000,000	86,400,000,000
Carrying value	0	0
Credit card merchant processing | Investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Credit card merchant processing | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Credit card merchant processing | Not rated
Maximum potential amount of future payments
Total amount outstanding	77,600,000,000	86,400,000,000
Credit card arrangements with partners
Maximum potential amount of future payments
Expire within 1 year	200,000,000	0
Expire after 1 year	1,300,000,000	1,500,000,000
Total amount outstanding	1,500,000,000	1,500,000,000
Carrying value	206,000,000	206,000,000
Credit card arrangements with partners | Investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Credit card arrangements with partners | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	0	0
Credit card arrangements with partners | Not rated
Maximum potential amount of future payments
Total amount outstanding	1,500,000,000	1,500,000,000
Custody indemnifications and other
Maximum potential amount of future payments
Expire within 1 year	1,500,000,000	0
Expire after 1 year	47,500,000,000	45,400,000,000
Total amount outstanding	49,000,000,000	45,400,000,000
Carrying value	58,000,000	58,000,000
Custody indemnifications and other | Investment grade
Maximum potential amount of future payments
Total amount outstanding	47,300,000,000	45,300,000,000
Custody indemnifications and other | Non-investment grade
Maximum potential amount of future payments
Total amount outstanding	100,000,000	100,000,000
Custody indemnifications and other | Not rated
Maximum potential amount of future payments
Total amount outstanding	1,600,000,000	0
Futures and over-the-counter derivatives clearing
Maximum potential amount of future payments
Amount of cash initial margin collected and remitted	$ 10,600,000,000	$ 9,400,000,000