Bonds Payable (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Bonds (Series A) [Member]
Total outstanding bonds	$ 69,747	$ 92,653
Maturity Date	Jul. 31, 2023
Bonds (Series B) [Member]
Total outstanding bonds	$ 61,029	60,764
Maturity Date	Jul. 31, 2025
Bonds (Series C) [Member]
Total outstanding bonds	$ 79,919	79,572
Maturity Date	Jan. 31, 2023
Bonds [Member]
Total outstanding bonds	$ 210,695	232,989
Less: unamortized deferred bond issuance costs	(7,503)	(9,724)
Total outstanding bonds, net	$ 203,192	$ 223,265

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

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