Income Tax (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Income tax expense	$ 0	$ 0	$ 0
Net losses	85,482	2,231	18,708
Estimated tax effect of claimed deductions		2,200
Tax payable	0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	69,700	50,600	57,200
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 68,900	$ 49,800	$ 56,400