Income Taxes Unrecognized Tax Benefits Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 3,370	$ 3,570	$ 4,610
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	2,800	3,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 1,700	$ 2,000
Minimum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2016
Maximum [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2010