Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 26, 2016	Mar. 27, 2016	Jun. 26, 2016	Sep. 27, 2015
Goodwill
Balance at beginning of the period			$ 601,379
Goodwill additions			104,454
Goodwill adjustments			8,377
Foreign exchange impact			13,563
Balance at end of the period	$ 727,773		727,773
CEG and Coffey
Goodwill
Goodwill adjustments	8,400
Coffey and INDUS
Goodwill
Balance at end of the period	110,831		110,831
WEI
Goodwill
Balance at beginning of the period			210,748
Goodwill additions			9,030
Foreign exchange impact			3,013
Balance at end of the period	222,791		222,791
Gross amounts of goodwill	305,200		305,200	$ 293,100
Accumulated impairment	82,400		82,400	82,400
WEI | Coffey and INDUS
Goodwill
Goodwill additions		$ 9,000
RME
Goodwill
Balance at beginning of the period			390,631
Goodwill additions			95,424
Goodwill adjustments			8,377
Foreign exchange impact			10,550
Balance at end of the period	504,982		504,982
Gross amounts of goodwill	538,200		538,200	423,800
Accumulated impairment	$ 33,200		$ 33,200	$ 33,200
RME | Coffey and INDUS
Goodwill
Goodwill additions		$ 101,800