Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period			$ 517,128
Total amount reclassified from Accumulated other comprehensive loss, net of tax	$ 2,022	$ 0	4,125	$ 0
Other comprehensive income (loss)	(11,140)	6,514	6,803	(15,007)
Balance at end of period	552,399		552,399
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(117,497)	(123,041)	(119,389)	(125,570)
Tax benefit	(1,042)	(1,477)	(2,086)	(2,894)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1,894	2,623	3,786	5,152
Balance at end of period	(115,603)	(120,418)	(115,603)	(120,418)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive loss	(90)	17	(180)	34
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive loss	3,026	4,083	6,052	8,012
Accumulated Foreign Currency Adjustment Attributable to Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(73,083)	(64,952)	(88,810)	(41,160)
Reclassification into earnings	1,252	0	3,355	0
Other comprehensive income (loss)	(15,042)	4,087	(1,418)	(19,705)
Balance at end of period	(86,873)	(60,865)	(86,873)	(60,865)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(3,292)	(2,457)	(3,616)	(2,199)
Reclassification into earnings	770		770
Other comprehensive income (loss)	(14)	(196)	310	(454)
Balance at end of period	$ (2,536)	$ (2,653)	$ (2,536)	$ (2,653)