Debt Financing Total Debt Financing (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Short Term Debt [Line Items]
Debt financing		$ 495,383,033	$ 451,496,716
Period End Rates		3.83%	3.60%
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term TOB [Member]
Short Term Debt [Line Items]
Debt financing		$ 46,860,699
Years Acquired		2014
Reset Frequency		N/A
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term TOB [Member] | Minimum [Member]
Short Term Debt [Line Items]
Stated Maturities		2017-07
Period End Rates		4.01%
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term TOB [Member] | Maximum [Member]
Short Term Debt [Line Items]
Stated Maturities		2019-07
Period End Rates		4.39%
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term A/B [Member]
Short Term Debt [Line Items]
Debt financing		$ 171,778,950
Restricted Cash		$ 1,373,695
Years Acquired		2016
TOB & Term A/B Trusts Securitization [Member] | Variable - TOB [Member]
Short Term Debt [Line Items]
Debt financing		$ 42,455,000
Years Acquired		2012
Stated Maturities		2016-12
Reset Frequency		Weekly
Facility Fees		1.62%
TOB & Term A/B Trusts Securitization [Member] | Variable - TOB [Member] | Minimum [Member]
Short Term Debt [Line Items]
Debt instrument variable rate		1.29%
Period End Rates		2.91%
TOB & Term A/B Trusts Securitization [Member] | Variable - TOB [Member] | Maximum [Member]
Short Term Debt [Line Items]
Debt instrument variable rate		1.39%
Period End Rates		3.01%
TEBS Financings [Member] | Variable - TEBS I [Member]
Short Term Debt [Line Items]
Debt financing		$ 60,430,991	$ 60,735,743
Restricted Cash		$ 396,412	$ 364,637
Years Acquired		2010	2010
Stated Maturities		2017-09	2017-09
Reset Frequency		Weekly	Weekly
Debt instrument variable rate		0.77%	0.04%
Facility Fees		1.85%	1.91%
Period End Rates		2.62%	1.95%
TEBS Financings [Member] | Variable - TEBS II [Member]
Short Term Debt [Line Items]
Debt financing	[1]	$ 91,768,081	$ 92,280,069
Restricted Cash	[1]	$ 170,988	$ 163,418
Years Acquired	[1]	2014	2014
Stated Maturities	[1]	2019-07	2019-07
Reset Frequency	[1]	Weekly	Weekly
Debt instrument variable rate	[1]	0.75%	0.02%
Facility Fees	[1]	1.62%	1.42%
Period End Rates	[1]	2.37%	1.44%
TEBS Financings [Member] | Variable - TEBS III [Member]
Short Term Debt [Line Items]
Debt financing	[1]	$ 82,089,312	$ 81,968,780
Restricted Cash	[1]	$ 3,495,592	$ 4,843,625
Years Acquired	[1]	2015	2015
Stated Maturities	[1]	2020-07	2020-07
Reset Frequency	[1]	Weekly	Weekly
Debt instrument variable rate	[1]	0.75%	0.02%
Facility Fees	[1]	1.39%	1.26%
Period End Rates	[1]	2.14%	1.28%
TOB Trusts Securitization [Member]
Short Term Debt [Line Items]
Debt financing			$ 160,582,124
TOB Trusts Securitization [Member] | Fixed - Term TOB [Member]
Short Term Debt [Line Items]
Debt financing			160,582,124
Restricted Cash			1,930,027
TOB Trusts Securitization [Member] | Variable - TOB [Member]
Short Term Debt [Line Items]
Debt financing			$ 55,930,000
Years Acquired			2012
Reset Frequency			Weekly
TOB Trusts Securitization [Member] | Variable - TOB [Member] | Minimum [Member]
Short Term Debt [Line Items]
Stated Maturities			2016-04
Debt instrument variable rate			0.16%
Facility Fees			0.94%
Period End Rates			1.10%
TOB Trusts Securitization [Member] | Variable - TOB [Member] | Maximum [Member]
Short Term Debt [Line Items]
Stated Maturities			2016-06
Debt instrument variable rate			0.68%
Facility Fees			1.62%
Period End Rates			2.30%

[1] Facility fees are variable