Segment Information - Revenue and Other Financial Information by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016
Segment Reporting Information [Line Items]
Revenue	$ 469,129	$ 434,055	$ 914,892	$ 788,923
Operating income	81,310	58,061	150,782	109,533
Depreciation and amortization	31,799	32,353	64,210	57,008
Capital expenditures	15,997	11,791	31,917	20,041
Operating segments
Segment Reporting Information [Line Items]
Operating income	114,310	94,947	217,282	181,778
Depreciation and amortization	29,697	30,243	60,120	53,426
Capital expenditures	13,445	11,281	26,663	19,170
RMS | Operating segments
Segment Reporting Information [Line Items]
Revenue	124,002	125,058	251,163	248,397
Operating income	33,579	35,445	71,290	71,831
Depreciation and amortization	4,945	5,118	10,037	10,368
Capital expenditures	4,404	2,381	7,007	3,434
DSA | Operating segments
Segment Reporting Information [Line Items]
Revenue	252,092	221,059	479,850	379,042
Operating income	51,690	32,381	90,350	63,211
Depreciation and amortization	18,965	18,600	38,334	30,557
Capital expenditures	7,102	4,644	15,425	9,351
Manufacturing | Operating segments
Segment Reporting Information [Line Items]
Revenue	93,035	87,938	183,879	161,484
Operating income	29,041	27,121	55,642	46,736
Depreciation and amortization	5,787	6,525	11,749	12,501
Capital expenditures	$ 1,939	$ 4,256	$ 4,231	$ 6,385