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SECURITIES - Unrealized Loss Position (Details) $ in Thousands | Jun. 30, 2020 USD ($) security | Dec. 31, 2019 USD ($) security
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Unrealized Loss Position For: |  |
Estimated fair value | $ 77,805,743 | $ 114,833,580
Gross unrealized losses | (203,273) | (291,441)
Agency Mortgage-Backed Securities |  |
Unrealized Loss Position For: |  |
Estimated fair value | 314,499 | 19,007,519
Gross unrealized losses | $ (289) | $ (129,385)
Number of securities | security | 9 | 491
Agency Mortgage-Backed Securities | Available For Sale Securities, Continuous Unrealized Loss Positions, Less Than 12 Months |  |
Unrealized Loss Position For: |  |
Estimated fair value | $ 312,936 | $ 7,388,239
Gross unrealized losses | $ (284) | $ (24,056)
Number of securities | security | 7 | 139
Agency Mortgage-Backed Securities | Available For Sale Securities, Continuous Unrealized Loss Positions, Greater Than 12 Months |  |
Unrealized Loss Position For: |  |
Estimated fair value | $ 1,563 | $ 11,619,280
Gross unrealized losses | $ (5) | $ (105,329)
Number of securities | security | 2 | 352

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- Definition Mortgage-Backed Securities in a continuous unrealized loss position [Line Items] + References No definition available. + Details
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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=118939692&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 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454 Reference 2: 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=118954083&loc=d3e26610-111562 Reference 3: 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=118939692&loc=d3e27161-111563 + Details
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