Goodwill and Intangible Assets (Goodwill Segment) (Details) $ in Thousands	6 Months Ended
	Jun. 24, 2016 USD ($)
Changes in goodwill
Balance at beginning of year	$ 510,985
Foreign currency translation	1,242
Balance at end of year	512,227
Environmental and Nuclear
Changes in goodwill
Balance at beginning of year	64,764
Foreign currency translation	3,027
Balance at end of year	67,791
Energy and Industrial
Changes in goodwill
Balance at beginning of year	93,242
Balance at end of year	93,242
Transportation
Changes in goodwill
Balance at beginning of year	281,520
Foreign currency translation	(1,424)
Balance at end of year	280,096
Water
Changes in goodwill
Balance at beginning of year	71,459
Foreign currency translation	(361)
Balance at end of year	$ 71,098