Fair Value of Financial Instruments (Level 3 Liabilities) (Details) - Level 3 - Recurring basis $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)
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	$ 1,041,283	$ 1,159,213
Issuances	0	0
Payment of principal	(245,451)	(363,146)
Changes in unrealized losses	(491)	(726)
Balance at end of period	795,341	795,341
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	979,541	1,124,162
Issuances	299,650	391,647
Payment of principal	(421,125)	(657,743)
Changes in unrealized losses	0	0
Balance at end of period	$ 858,066	$ 858,066

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Principal Paydowns

No definition available.

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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

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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.

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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

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- Definition

Fair value 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)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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