Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Changes in accumulated other comprehensive income [Roll Forward]
Balance			$ 441,028
Other comprehensive income before reclassifications	$ 3,016		5,739
Amounts reclassified from accumulated other comprehensive income	(163)		(198)
Total other comprehensive income (loss), net of tax	2,853	$ (1,700)	5,541	$ 243
Balance	472,224		472,224
AOCI Attributable to Parent [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance	(8,340)		(11,028)
Total other comprehensive income (loss), net of tax			5,541
Balance	(5,487)		(5,487)
Foreign Currency Translation Adjustments [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance	(8,529)		(11,252)
Other comprehensive income before reclassifications	2,733		5,456
Amounts reclassified from accumulated other comprehensive income	0		0
Total other comprehensive income (loss), net of tax	2,733		5,456
Balance	(5,796)		(5,796)
Unrecognized Postretirement Benefit Costs (Credit) [Member]
Changes in accumulated other comprehensive income [Roll Forward]
Balance	189		224
Other comprehensive income before reclassifications	283		283
Amounts reclassified from accumulated other comprehensive income	(163)		(198)
Total other comprehensive income (loss), net of tax	120		85
Balance	$ 309		$ 309