Accumulated Other Comprehensive Income (Loss) and Shareholders' Equity (Components) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 500,603
Other comprehensive income (loss) before reclassifications	376	$ (3,167)
Tax (expense) or benefit	(150)	(916)
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	(207)	(453)
Ending balance	495,463
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(5,000)	(5,186)
Ending balance	(4,267)	(6,984)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,188)	322
Other comprehensive income (loss) before reclassifications	779	(678)
Tax (expense) or benefit	0	0
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	0	0
Ending balance	(409)	(356)
Unrealized Gains (Losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(105)	(2)
Other comprehensive income (loss) before reclassifications	68	17
Tax (expense) or benefit	24	6
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	0	0
Ending balance	(61)	9
Pension and Post-retirement Liabilities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(5,167)	(5,506)
Other comprehensive income (loss) before reclassifications	0	0
Tax (expense) or benefit	0	0
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	0	0
Ending balance	(5,167)	(5,506)
Derivative Financial Instruments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	1,460	0
Other comprehensive income (loss) before reclassifications	(471)	(2,506)
Tax (expense) or benefit	(174)	(922)
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	(207)	(453)
Ending balance	$ 1,370	$ (1,131)