Income Taxes (Reconciliation of Gross Unrecognized Tax Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of gross unrecognized tax benefits
Gross unrecognized tax benefit balance at beginning of year	$ 7,574	$ 3,612	$ 7,636
Change in tax positions of prior years		3,543
Change in tax positions of prior years	(1,207)		(3,073)
Change in tax positions of current year	128	419	169
Reduction in tax positions for statute expirations			(1,120)
Gross unrecognized tax benefit balance at end of year	$ 6,495	$ 7,574	$ 3,612