Debt Financing - Schedule of Total Debt Financing (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Short Term Debt [Line Items]
Debt financing		$ 558,328,347	$ 495,383,033
Period End Rates		4.21%	3.83%
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term TOB [Member]
Short Term Debt [Line Items]
Debt financing		$ 46,787,036	$ 46,860,699
Year Acquired		2014
Stated Maturities		2019-10
Reset Frequency		N/A	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%	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%	4.39%
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term A/B [Member]
Short Term Debt [Line Items]
Debt financing		$ 279,533,565	$ 171,778,950
Restricted Cash			$ 1,373,695
Year Acquired			2016
Reset Frequency		N/A	N/A
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term A/B [Member] | Minimum [Member]
Short Term Debt [Line Items]
Year Acquired		2016
Stated Maturities		2018-06	2017-03
Period End Rates		3.64%	3.64%
TOB & Term A/B Trusts Securitization [Member] | Fixed - Term A/B [Member] | Maximum [Member]
Short Term Debt [Line Items]
Year Acquired		2017
Stated Maturities		2027-11	2026-12
Period End Rates		4.52%	4.56%
TOB & Term A/B Trusts Securitization [Member] | Variable - TOB [Member]
Short Term Debt [Line Items]
Debt financing		$ 38,130,000	$ 42,455,000
Restricted Cash		$ 850,327
Year Acquired		2012	2012
Stated Maturities		2018-05	2016-12
Reset Frequency		Weekly	Weekly
Facility Fees		1.67%	1.62%
TOB & Term A/B Trusts Securitization [Member] | Variable - TOB [Member] | Minimum [Member]
Short Term Debt [Line Items]
SIFMA Based Rates		2.24%	1.29%
Period End Rates		3.91%	2.91%
TOB & Term A/B Trusts Securitization [Member] | Variable - TOB [Member] | Maximum [Member]
Short Term Debt [Line Items]
SIFMA Based Rates		2.29%	1.39%
Period End Rates		3.96%	3.01%
TEBS Financings [Member] | Variable - TEBS I [Member]
Short Term Debt [Line Items]
Debt financing		$ 55,468,000	$ 60,430,991
Restricted Cash		$ 372,222	$ 396,412
Year Acquired		2010	2010
Stated Maturities		2020-09	2017-09
Reset Frequency		Weekly	Weekly
SIFMA Based Rates		1.79%	0.77%
Facility Fees		1.85%	1.85%
Period End Rates		3.64%	2.62%
TEBS Financings [Member] | Variable - TEBS II [Member]
Short Term Debt [Line Items]
Debt financing	[1]	$ 81,003,688	$ 91,768,081
Restricted Cash	[1]	$ 176,685	$ 170,988
Year Acquired	[1]	2014	2014
Stated Maturities	[1]	2019-07	2019-07
Reset Frequency	[1]	Weekly	Weekly
SIFMA Based Rates	[1]	1.77%	0.75%
Facility Fees	[1]	1.39%	1.62%
Period End Rates	[1]	3.16%	2.37%
TEBS Financings [Member] | Variable - TEBS III [Member]
Short Term Debt [Line Items]
Debt financing	[1]	$ 57,406,058	$ 82,089,312
Restricted Cash	[1]	$ 57,364	$ 3,495,592
Year Acquired	[1]	2015	2015
Stated Maturities	[1]	2020-07	2020-07
Reset Frequency	[1]	Weekly	Weekly
SIFMA Based Rates	[1]	1.77%	0.75%
Facility Fees	[1]	1.16%	1.39%
Period End Rates	[1]	2.93%	2.14%

[1] Facility fees have a variable component.