Fair Value of Assets and Liabilities - Investments in small business investment companies (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)
Fair Value of Assets and Liabilities
Fair value of investment in small business investment companies	$ 1,430	$ 1,430
Unrealized losses	$ 124	$ 124

Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

Name:	us-gaap_EquitySecuritiesFvNiUnrealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration