Summary of Significant Accounting Policies - Amortization Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible assets subject to amortization	$ 3,458	$ 3,458
Less accumulated amortization	237	0
Intangible assets subject to amortization, net	3,221	3,458
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible assets subject to amortization	3,410	3,410
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount of intangible assets subject to amortization	$ 48	$ 48