Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 0	$ 0	$ 0
Net income (loss)	25,270,000	(14,345,000)	(85,482,000)
Estimated tax effect of claimed deductions	2,200,000
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	3,700,000	69,600,000	75,700,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 14,900,000	$ 36,700,000	$ 68,900,000