Shareholders' Equity and Accumulated Other Comprehensive Income - Accumulated Other Comprehensive Income (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 28, 2019	Jun. 29, 2018	Mar. 30, 2018	Jun. 28, 2019	Jun. 29, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Foreign currency translation adjustments and other	$ 1,329	$ (11,969)		$ (1,588)	$ (5,955)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	642,167	642,329	$ 635,656	633,157	635,656
Other comprehensive income (loss)	4,265	(9,766)		4,284	(1,535)
Ending balance	$ 658,169	642,772	$ 642,329	$ 658,169	$ 642,772
Common Stock, Dividends, Per Share, Declared	$ 0		$ 0	$ 0	$ 0
Total accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Ending balance	$ (153,708)	(117,349)		$ (153,708)	$ (117,349)
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(17,496)	(1,040)	$ (7,054)	(14,579)	(7,054)
OCI, before Reclassifications		(11,969)
Other comprehensive income (loss)	1,329	(11,969)		(1,588)	(5,955)
Ending balance	(16,167)	(13,009)	(1,040)	(16,167)	(13,009)
Pension and other post-retirement benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI, Current Period, Net of Tax, Attributable to Parent	2,936	2,203		5,872	4,420
Cumulative Effect on Retained Earnings, Tax				23,094	0
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(140,477)	(106,543)	(108,760)	(120,319)	(108,760)
Other comprehensive income (loss)	2,936	2,203		5,872	4,420
Ending balance	(137,541)	(104,340)	$ (106,543)	(137,541)	(104,340)
Amortization of net loss, net of tax expense	$ 940	$ 703		$ 1,880	$ 1,413