INVESTMENT SECURITIES AND OTHER SECURITIES - Narrative (Details) - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Mar. 31, 2019 |
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| Investments, Debt and Equity Securities [Abstract] | ||
| Pledged Financial Instruments, Not Separately Reported, Securities for Other Debt Facilities | $ 5,000,000,000 | $ 4,000,000,000 |
| Other-than-temporary Impairment Loss, Debt Securities, Portion Recognized in Earnings | 0 | |
| Other-than-temporary Impairment Loss, Equity Securities, Portion Recognized in Earnings | $ 0 |
| X | ||||||||||
- Definition Other-than-temporary Impairment Loss, Equity Securities, Portion Recognized in Earnings No definition available.
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| X | ||||||||||
- References No definition available.
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| X | ||||||||||
- Definition Amount of other-than-temporary impairment (OTTI) on investment in debt security, recognized in earnings. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for debt facilities other than FHLB loans, repurchase agreements and letter of credit arrangements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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