CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016
Income Statement [Abstract]
Service revenue	$ 329,398	$ 292,847	$ 633,929	$ 513,548
Product revenue	139,731	141,208	280,963	275,375
Total revenue	469,129	434,055	914,892	788,923
Costs and expenses:
Cost of services provided (excluding amortization of intangible assets)	214,716	196,121	421,536	343,470
Cost of products sold (excluding amortization of intangible assets)	68,751	68,187	135,995	134,938
Selling, general and administrative	94,533	100,473	186,023	183,417
Amortization of intangible assets	9,819	11,213	20,556	17,565
Operating income	81,310	58,061	150,782	109,533
Other income (expense):
Interest income	161	222	363	485
Interest expense	(7,403)	(8,909)	(14,386)	(13,120)
Other income, net	2,848	5,016	18,204	9,042
Income from continuing operations, before income taxes	76,916	54,390	154,963	105,940
Provision for income taxes	22,243	18,845	53,327	32,820
Income from continuing operations, net of income taxes	54,673	35,545	101,636	73,120
Income (loss) from discontinued operations, net of income taxes	(71)	12	(75)	(14)
Net income	54,602	35,557	101,561	73,106
Less: Net income attributable to noncontrolling interests	650	350	831	756
Net income attributable to common shareholders	$ 53,952	$ 35,207	$ 100,730	$ 72,350
Basic:
Continuing operations attributable to common shareholders (in dollars per share)	$ 1.14	$ 0.75	$ 2.12	$ 1.54
Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.00
Net income attributable to common shareholders (in dollars per share)	1.13	0.75	2.12	1.54
Diluted:
Continuing operations attributable to common shareholders (in dollars per share)	1.12	0.73	2.08	1.51
Discontinued operations (in dollars per share)	0.00	0.00	0.00	0.00
Net income attributable to common shareholders (in dollars per share)	$ 1.12	$ 0.73	$ 2.08	$ 1.51