Income Taxes - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Dec. 22, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 16, 2014
Operating Loss Carryforwards [Line Items]
Projected annual limitation on the use of the net operating losses that existed prior to September 17, 2014													$ 800
Profit (loss) from operations		$ 5,995	$ (1,336)	$ (4,246)	$ (4,322)	$ (4,031)	$ (2,521)	$ (9,623)	$ 1,191	$ (3,909)	$ (14,984)	$ (19,245)
Increase (decrease) in valuation allowance										1,700
Change in valuation allowance										1,688	$ (5,445)	$ 7,677
Tax Cuts and Jobs Act of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense	$ 11,700
Federal | Internal Revenue Service
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards		44,600								44,600
Profit (loss) from operations										1,300
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards		$ 25,200								$ 25,200