Income Taxes - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Income tax receivable	$ 8,371,000		$ 8,371,000
Tax Cuts And Jobs Act Of 2017, change in tax rate, deferred tax asset, income tax benefit			33,500,000
Deferred tax assets, valuation allowance	4,900,000		5,000,000
Unrecognized tax benefits	2,100,000		2,100,000
Unrecognized tax benefits, that would impact effective tax rate	0		0
Unrecognized tax benefits, period increase (decrease)	0	$ 0
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	0		0
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	388,700,000		391,700,000
Alternative Minimum Tax Credit Carryforward | Federal
Operating Loss Carryforwards [Line Items]
Income tax receivable	$ 8,400,000		$ 8,400,000