Goodwill and Intangible Assets (Intangible Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 25, 2015	Sep. 30, 2016	Sep. 25, 2015
Changes in intangibles
Balance at beginning of year			$ 59,011
Amortization	$ (4,400)	$ (6,200)	(13,924)	$ (19,700)
Foreign currency translation			(1,176)
Balance at end of year	43,911		43,911
Environmental and Nuclear
Changes in intangibles
Balance at beginning of year			30,096
Amortization			(3,489)
Foreign currency translation			1,399
Balance at end of year	28,006		28,006
Transportation
Changes in intangibles
Balance at beginning of year			22,731
Amortization			(8,148)
Foreign currency translation			(1,955)
Balance at end of year	12,628		12,628
Water
Changes in intangibles
Balance at beginning of year			6,184
Amortization			(2,287)
Foreign currency translation			(620)
Balance at end of year	$ 3,277		$ 3,277