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Fair Value of Financial Instruments - Valuation for Level 3 Assets (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |
Balance at beginning of period | $ 9,835,319 | $ 7,061,842 |
Total (losses)/gains (realized/unrealized) |  |  |
Included in earnings | (182,601) | 3,340 |
Included in other comprehensive income (loss) | (4) | (193) |
Contributions | 0 | 1,300 |
Paydowns/Distributions | (38,530) | (38,425) |
Purchases | 15,966 | 1,545,030 |
Balance at the end of period | 9,630,150 | 8,572,894 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Assets of consolidated VIEs | $ 9,771,205 |  | $ 10,041,468
Consolidated K-Series |  |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |  |
Assets of consolidated VIEs |  | $ 1,500,000 |

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- Definition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Contributions + References No definition available. + Details
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- Definition Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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