Segment Information - Revenue and Other Financial Information by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 24, 2016	Sep. 30, 2017	Sep. 24, 2016
Segment Reporting Information [Line Items]
Revenue	$ 464,232	$ 425,720	$ 1,379,124	$ 1,214,643
Operating income	73,984	58,795	224,766	168,328
Depreciation and amortization	33,465	34,108	97,675	91,116
Capital expenditures	22,011	9,568	53,928	29,609
Operating segments
Segment Reporting Information [Line Items]
Operating income	109,265	89,238	326,547	271,016
Depreciation and amortization	31,177	32,097	91,297	85,523
Capital expenditures	19,768	8,903	46,432	28,073
RMS | Operating segments
Segment Reporting Information [Line Items]
Revenue	122,020	120,928	373,183	369,325
Operating income	30,726	31,224	102,016	103,055
Depreciation and amortization	5,272	5,245	15,309	15,613
Capital expenditures	6,762	2,532	13,769	5,966
DSA | Operating segments
Segment Reporting Information [Line Items]
Revenue	246,946	215,817	726,796	594,859
Operating income	46,616	31,303	136,966	94,514
Depreciation and amortization	20,333	20,671	58,667	51,228
Capital expenditures	10,127	4,509	25,552	13,860
Manufacturing | Operating segments
Segment Reporting Information [Line Items]
Revenue	95,266	88,975	279,145	250,459
Operating income	31,923	26,711	87,565	73,447
Depreciation and amortization	5,572	6,181	17,321	18,682
Capital expenditures	$ 2,879	$ 1,862	$ 7,111	$ 8,247