Comprehensive Income (Changes in Accumulated Other Comprehensive Loss by Component) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 112,143	$ 837,656
Other comprehensive income (loss) before reclassifications	207
Amounts reclassified from accumulated other comprehensive loss	(1,943)
Other comprehensive loss	(1,736)	(2,683)
Ending balance	249,692	(218,929)
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(2,946)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive loss	0
Ending balance	(2,946)
Unrealized Net (Loss) Gains on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(18)
Other comprehensive income (loss) before reclassifications	20
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive loss	20
Ending balance	2
Unrealized Gain on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	3,562
Other comprehensive income (loss) before reclassifications	(863)
Amounts reclassified from accumulated other comprehensive loss	(1,943)
Other comprehensive loss	(2,806)
Ending balance	756
Other Comprehensive Loss on Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4,247)
Other comprehensive income (loss) before reclassifications	1,050
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive loss	1,050
Ending balance	(3,197)
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(3,649)	(5,127)
Other comprehensive loss	(1,736)	(2,683)
Ending balance	$ (5,385)	$ (7,810)