Income Taxes - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Consolidated effective tax rate	109.70%	(77.50%)	23.80%
Federal statutory tax rate		35.00%	35.00%
Deferred tax liabilities, provisional income tax benefit	$ 5,900
Deferred tax liabilities, provisional income tax benefit (in usd per share)	$ 0.21
Valuation allowance	$ 3,942	$ 3,321
Alternative minimum tax credits, non-expiring	700
Balance at the end of year	1,614	0
Deferred tax assets, net, noncurrent		$ 2,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	5,700
Federal Tax Authority
Operating Loss Carryforwards [Line Items]
Alternative minimum tax credits, non-expiring	$ 1,200