Segment Information - Operating Results Information for Each Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended							9 Months Ended	12 Months Ended
	Oct. 02, 2015	Apr. 03, 2015	Jan. 02, 2015	Sep. 26, 2014	Jun. 27, 2014	Mar. 28, 2014	Dec. 27, 2013	Jul. 03, 2015	Oct. 02, 2015	Sep. 26, 2014	Sep. 27, 2013
Segment Reporting Information [Line Items]
Revenues	$ 817,800	$ 759,400	$ 737,900	$ 812,100	$ 747,700	$ 778,500	$ 711,500	$ 784,000	$ 3,099,111	$ 3,049,800	$ 2,942,897
Operating Earnings									548,967	571,155	608,890
Depreciation & Amortization									68,500	62,500	62,900
Total Assets	3,600,748			3,357,290					3,600,748	3,357,290	3,468,500
Corporate
Segment Reporting Information [Line Items]
Operating Earnings									(36,500)	(41,500)	(22,300)
Depreciation & Amortization									20,700	22,000	25,900
Total Assets	1,336,600			1,333,000					1,336,600	1,333,000	1,574,900
Operating Segments | Oncology Systems
Segment Reporting Information [Line Items]
Revenues									2,344,000	2,344,200	2,252,700
Operating Earnings									485,400	495,500	512,000
Depreciation & Amortization									27,200	24,800	21,000
Total Assets	1,412,500			1,314,100					1,412,500	1,314,100	1,217,000
Operating Segments | Imaging Components
Segment Reporting Information [Line Items]
Revenues									611,200	660,200	641,900
Operating Earnings									131,300	169,900	165,600
Depreciation & Amortization									15,700	14,700	14,600
Total Assets	555,400			431,600					555,400	431,600	398,500
Operating Segments | Total reportable segments
Segment Reporting Information [Line Items]
Revenues									2,955,200	3,004,400	2,894,600
Operating Earnings									616,700	665,400	677,600
Depreciation & Amortization									42,900	39,500	35,600
Total Assets	1,967,900			1,745,700					1,967,900	1,745,700	1,615,500
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues									143,900	45,400	48,300
Operating Earnings									(31,200)	(52,700)	(46,400)
Depreciation & Amortization									4,900	1,000	1,400
Total Assets	$ 296,200			$ 278,600					$ 296,200	$ 278,600	$ 278,100