Intangible Assets - Assets subject to amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 3,458	$ 3,458
Less accumulated amortization	(533)	(474)
Intangible assets subject to amortization, net	2,925	2,984
Trade names
Finite-Lived Intangible Assets [Line Items]
Intangible assets	3,410	3,410
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 48	$ 48