Segment Reporting Information - Operations and Assets (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2020 USD ($)	Jun. 28, 2019 USD ($)	Jun. 26, 2020 USD ($) segment	Jun. 28, 2019 USD ($)	Dec. 27, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			3
Revenues	$ 366,892	$ 428,328	$ 740,459	$ 833,198
Operating Earnings	44,773	112,361	134,585	216,888
Total Assets	1,962,459		1,962,459		$ 1,692,210
Operating Segments | Industrial
Segment Reporting Information [Line Items]
Revenues	133,287	188,507	291,971	377,607
Operating Earnings	37,001	64,428	87,234	129,631
Total Assets	621,314		621,314		615,486
Operating Segments | Process
Segment Reporting Information [Line Items]
Revenues	77,759	85,064	163,837	171,958
Operating Earnings	11,672	18,378	29,783	38,392
Total Assets	403,083		403,083		387,216
Operating Segments | Contractor
Segment Reporting Information [Line Items]
Revenues	155,846	154,757	284,651	283,633
Operating Earnings	41,109	40,054	69,739	66,593
Total Assets	420,983		420,983		368,832
Unallocated corporate
Segment Reporting Information [Line Items]
Operating Earnings	(10,047)	(10,499)	(17,209)	(17,728)
Impairment - Segment Information	(34,962)	$ 0	(34,962)	$ 0
Total Assets	$ 517,079		$ 517,079		$ 320,676