Debt Financing Summary of Tax Exempt Bonds Securitization (Details) - USD ($)		3 Months Ended	12 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Debt financing		$ 430,307,422	$ 451,496,716
Period End Rate		3.73%	3.58%
Tax Exempt Bond Securitization [Member]
Debt Instrument [Line Items]
Debt financing		$ 235,003,503	$ 234,984,592
Period End Rate		1.94%	1.51%
Tax Exempt Bond Securitization [Member] | M24 TEBS Financing [Member]
Debt Instrument [Line Items]
Debt financing		$ 60,787,787	$ 60,735,743
Year Acquired		2010	2010
Stated Maturity		2017-09	2017-09
Variable / Fixed		Variable	Variable
Reset Frequency		Weekly	Weekly
SIFMA Based Rate		0.46%	0.04%
Facility Fees		1.91%	1.91%
Period End Rate		2.37%	1.95%
Tax Exempt Bond Securitization [Member] | M31 TEBS Financing [Member]
Debt Instrument [Line Items]
Debt financing	[1]	$ 92,191,475	$ 92,280,069
Year Acquired	[1]	2014	2014
Stated Maturity	[1]	2019-07	2019-07
Variable / Fixed	[1]	Variable	Variable
Reset Frequency	[1]	Weekly	Weekly
SIFMA Based Rate	[1]	0.44%	0.02%
Facility Fees	[1]	1.42%	1.42%
Period End Rate	[1]	1.86%	1.44%
Tax Exempt Bond Securitization [Member] | M33 TEBS Financing [Member]
Debt Instrument [Line Items]
Debt financing	[1]	$ 82,024,241	$ 81,968,780
Year Acquired	[1]	2015	2015
Stated Maturity	[1]	2020-07	2020-07
Variable / Fixed	[1]	Variable	Variable
Reset Frequency	[1]	Weekly	Weekly
SIFMA Based Rate	[1]	0.44%	0.02%
Facility Fees	[1]	1.26%	1.26%
Period End Rate	[1]	1.70%	1.28%

[1] Facility fees are variable