Changes in Accumulated Other Comprehensive Income (Loss) - Summary (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	$ 353,396
Other Comprehensive (loss) income	(8,529)	$ 14,469
Amounts reclassified from accumulated other comprehensive loss	397	344
Balance at end of period	370,715
Loss reclassified from AOCI for defined benefit pension plans	400	300
Tax benefit reclassified from AOCI for defined benefit pension plans	10	200
Total Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(20,148)	(47,950)
Balance at end of period	(28,280)	(33,137)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(2,221)	(27,885)
Other Comprehensive (loss) income	(8,604)	14,513
Amounts reclassified from accumulated other comprehensive loss	0	0
Balance at end of period	(10,825)	(13,372)
Defined Benefit Pension Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(18,049)	(20,065)
Other Comprehensive (loss) income	0	0
Amounts reclassified from accumulated other comprehensive loss	397	344
Balance at end of period	(17,652)	(19,721)
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	122	0
Other Comprehensive (loss) income	75	(44)
Amounts reclassified from accumulated other comprehensive loss	0	0
Balance at end of period	$ 197	$ (44)