Income Taxes Income Tax Provision Included in Other Income Expense on Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Federal	$ 0	$ 132	$ 305
State	422	341	35
Federal	0	0	0
State	(208)	93	(45)
Provision for income taxes	$ 214	$ 566	$ 295