Long-Term Debt - Narrative (Details)		3 Months Ended		6 Months Ended
	Dec. 29, 2017 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Revenues		$ 6,677,000	$ 1,274,000	$ 11,153,000	$ 2,139,000
Interest expense amortization period				5 years 6 months
Interest expense, back end fees				$ 2,000,000
Debt issuance costs							$ 2,181,000
Senior Notes
Debt Instrument [Line Items]
Interest expense, front end fees				1,000,000
Senior Notes | Note Purchase Agreement
Debt Instrument [Line Items]
Unused borrowing capacity, amount	$ 100,000,000
Face amount	$ 75,000,000	$ 75,000,000		$ 75,000,000		$ 75,000,000
Stated interest rate	9.00%	11.4375%		11.4375%
Upfront fee (as a percent)	1.00%
Exit fee (as a percent)	2.00%
Prepayment, prior to second anniversary	102.00%
Prepayment fee, after second and before third anniversary	2.00%
Prepayment fee, after third and before fourth anniversary	1.00%
Interest expense		$ 2,389,000	$ 2,301,000	$ 4,777,000	$ 4,494,000
Senior Notes | Note Purchase Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Interest rate floor (as a percent)	1.00%
Senior Notes | Note Purchase Agreement - Delayed Draw Notes
Debt Instrument [Line Items]
Unused borrowing capacity, amount	$ 25,000,000
Revenues	$ 15,000,000
Total debt to trailing four quarter net revenues	6.50