Fair Value of Financial Instruments - Quantitative Information About Significant Unobservable Inputs (Details) - Level 3 - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Equity warrant asset, public portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 1,166	$ 346
Equity warrant assets, private portfolio
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	191,517	160,692
Unconsolidated venture capital and private equity fund investments
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair value	$ 134	$ 134

Fair value of 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.

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=117815213&loc=d3e19207-110258

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant