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SECURITIES - Unrealized Loss Position (Details) $ in Thousands | Dec. 31, 2019 USD ($) security | Dec. 31, 2018 USD ($) security
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Unrealized Loss Position For: |  |
Estimated fair value | $ 114,833,580 | $ 92,623,788
Gross unrealized losses | (291,441) | (2,609,491)
Agency Mortgage-Backed Securities |  |
Unrealized Loss Position For: |  |
Estimated fair value | 19,007,519 | 65,552,879
Gross unrealized losses | $ (129,385) | $ (2,285,609)
Number of securities | security | 491 | 2,189
Available For Sale Securities, Continuous Unrealized Loss Positions, Less Than 12 Months | Agency Mortgage-Backed Securities |  |
Unrealized Loss Position For: |  |
Estimated fair value | $ 7,388,239 | $ 22,418,036
Gross unrealized losses | $ (24,056) | $ (432,352)
Number of securities | security | 139 | 713
Available For Sale Securities, Continuous Unrealized Loss Positions, Greater Than 12 Months | Agency Mortgage-Backed Securities |  |
Unrealized Loss Position For: |  |
Estimated fair value | $ 11,619,280 | $ 43,134,843
Gross unrealized losses | $ (105,329) | $ (1,853,257)
Number of securities | security | 352 | 1,476

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- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563 + Details
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