Comprehensive Income (Changes in Accumulated Other Comprehensive Loss by Component) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	$ (10,806)
Other comprehensive loss before reclassifications	(3,850)
Amounts reclassified from accumulated other comprehensive loss	(218)
Other comprehensive (loss) income	(4,068)	$ 4,370
Balance at March 31, 2018	(14,874)
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	(2,946)
Other comprehensive loss before reclassifications	0
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive (loss) income	0
Balance at March 31, 2018	(2,946)
Unrealized Loss on Available-for-sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	(6,666)
Other comprehensive loss before reclassifications	(4,542)
Amounts reclassified from accumulated other comprehensive loss	1,001
Other comprehensive (loss) income	(3,541)
Balance at March 31, 2018	(10,207)
Unrealized (Loss) Gain on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	2,158
Other comprehensive loss before reclassifications	692
Amounts reclassified from accumulated other comprehensive loss	(1,219)
Other comprehensive (loss) income	(527)
Balance at March 31, 2018	1,631
Other Comprehensive Loss on Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017	(3,352)
Other comprehensive loss before reclassifications	0
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive (loss) income	0
Balance at March 31, 2018	$ (3,352)