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Fair Value of Financial Instruments (Level 3 Liabilities) (Details) - Level 3 - Recurring basis - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
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Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020
Agreements with Non-mark-to-market Collateral Provisions |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Balance at beginning of period | $ 795,341 | $ 0 | $ 1,159,213 | $ 0
Issuances | 0 | 2,036,597 | 0 | 2,036,597
Payment of principal | (104,549) | (312,638) | (467,695) | (312,638)
Changes in unrealized losses | (209) | 3,448 | (935) | 3,448
Balance at end of period | 690,583 | 1,727,407 | 690,583 | 1,727,407
Agreements with Mark-to-market Collateral Provisions |  |  |  |
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Balance at beginning of period | 858,066 | 0 | 1,124,162 | 0
Issuances | 597,761 | 1,386,592 | 989,407 | 1,386,592
Payment of principal | (180,655) | (156,032) | (838,397) | (156,032)
Changes in unrealized losses | 0 | 1,174 | 0 | 1,174
Balance at end of period | $ 1,275,172 | $ 1,231,734 | $ 1,275,172 | $ 1,231,734

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- Definition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Principal Paydowns + References No definition available. + Details
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- Definition Amount of unrealized gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3) and still held. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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- Definition Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
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