Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (259,817)	$ (219,205)	$ (266,649)	$ (212,949)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2,653)	18,359
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	7,525	(25,151)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	1,960	536
Other Comprehensive Income (Loss), Net of Tax	6,832	(6,256)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(46,480)	(30,901)	(57,394)	(4,960)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	10,914	(25,941)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0
Other Comprehensive Income (Loss), Net of Tax	10,914	(25,941)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(1,168)	12,881	3,016	(1,944)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2,653)	18,359
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(554)	(1,547)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(977)	(1,987)
Other Comprehensive Income (Loss), Net of Tax	(4,184)	14,825
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(212,169)	(201,185)	$ (212,271)	$ (206,045)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(2,835)	2,337
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2,937	2,523
Other Comprehensive Income (Loss), Net of Tax	$ 102	$ 4,860