Debt and Other Obligations - Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Debt Instrument [Line Items]
Amortization of deferred financing costs	$ 2,192	$ 1,491
Interest Expense, Other	74	77
Total	24,971	17,849
Senior Loans [Member]
Debt Instrument [Line Items]
Interest expense, term loans	3,945	4,317
Junior Loans [Member]
Debt Instrument [Line Items]
Interest expense, term loans	523	667
Fixed Rate Loan [Member]
Debt Instrument [Line Items]
Interest expense, term loans	6,202	4,911
Equipment Notes, Series A 2015-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	3,838	4,142
Equipment Notes, Series B 2015-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	880	1,012
Equipment Notes, Series C 2015-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	1,335	0
Equipment Notes, Series AA 2017-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	1,989	682
Equipment Notes, Series A 2017-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	717	246
Equipment Notes, Series B 2017-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	754	283
Equipment Notes, Series C 2017-1 [Member]
Debt Instrument [Line Items]
Interest expense, term loans	1,080	0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense, term loans	1,413	0
Finance Lease Obligations [Member]
Debt Instrument [Line Items]
Interest expense, term loans	$ 29	$ 21