Fair Value of Financial Instruments - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impairment charge	$ 150,000	$ 150,000
Gardner, KS [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Impairment charge	$ 150,000
Taxable Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	9.10%	9.10%
MRBs and Bond Purchase Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Weighted average effective yield	4.90%	4.90%
Effective rate - minimum [Member] | Taxable Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Effective rate	8.30%	8.30%	7.90%
Effective rate - minimum [Member] | MRBs and Bond Purchase Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Effective rate	3.50%	3.50%	2.90%
Effective rate - maximum [Member] | Taxable Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Effective rate	9.50%	9.50%	9.20%
Effective rate - maximum [Member] | MRBs and Bond Purchase Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Effective rate	9.30%	9.30%	8.80%