Comprehensive Income (Changes in Accumulated Other Comprehensive Loss by Component) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017			$ (10,806)
Other comprehensive loss before reclassifications			(6,940)
Amounts reclassified from accumulated other comprehensive loss			(972)
Other comprehensive (loss) income	$ (3,844)	$ 2,155	(7,912)	$ 6,525
Balance at June 30, 2018	(18,718)		(18,718)
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 June 30, 2018	(2,946)		(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			(4,210)
Amounts reclassified from accumulated other comprehensive loss			1,244
Other comprehensive (loss) income			(2,966)
Balance at June 30, 2018	(9,632)		(9,632)
Unrealized Gain (Loss) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at December 31, 2017			2,158
Other comprehensive loss before reclassifications			(2,730)
Amounts reclassified from accumulated other comprehensive loss			(2,216)
Other comprehensive (loss) income			(4,946)
Balance at June 30, 2018	(2,788)		(2,788)
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 June 30, 2018	$ (3,352)		$ (3,352)