Debt (Schedule of Cash Paid for Interest) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Long-term Debt, Unclassified [Abstract]
Interest expense, net	$ (220)	$ (217)	$ (222)	$ (44)	$ 5	$ (79)	$ (249)	$ (2,000)	$ (703)	$ (2,323)	$ (10,709)
Interest income									276	764	2,156
Other non-cash adjustments									(345)	(380)	(529)
Cash paid for interest									$ 634	$ 2,707	$ 12,336