Income Tax Income Tax - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Tax Cuts And Jobs Act Of 2017, provisional income tax benefit	$ 4,900
Net deferred tax (liability) asset	(7,009)	$ (5,041)
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	2,300
Operating loss carryforwards	12,600
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 7,100