Segment Information - Operating Results Information for Each Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Jan. 01, 2016	Oct. 02, 2015	Jul. 03, 2015	Apr. 03, 2015	Jan. 02, 2015	Sep. 30, 2016	Oct. 02, 2015	Sep. 26, 2014
Segment Reporting Information [Line Items]
Revenues	$ 912.5	$ 789.4	$ 758.8	$ 757.1	$ 817.8	$ 784.0	$ 759.4	$ 737.9	$ 3,217.8	$ 3,099.1	$ 3,049.8
Operating Earnings									550.8	549.0	571.2
Depreciation & Amortization									79.8	68.5	62.5
Total Assets	3,816.0				3,578.7				3,816.0	3,578.7	3,338.7
Corporate
Segment Reporting Information [Line Items]
Revenues									0.0	0.0	0.0
Operating Earnings									(61.5)	(36.5)	(41.5)
Depreciation & Amortization									19.6	20.7	22.0
Total Assets	1,367.0				1,314.6				1,367.0	1,314.6	1,314.4
Operating Segments | Oncology Systems
Segment Reporting Information [Line Items]
Revenues									2,457.1	2,344.0	2,344.2
Operating Earnings									550.5	485.4	495.5
Depreciation & Amortization									33.8	27.2	24.8
Total Assets	1,491.2				1,412.5				1,491.2	1,412.5	1,314.1
Operating Segments | Imaging Components
Segment Reporting Information [Line Items]
Revenues									597.6	611.2	660.2
Operating Earnings									110.7	131.3	169.9
Depreciation & Amortization									19.0	15.7	14.7
Total Assets	587.9				555.4				587.9	555.4	431.6
Operating Segments | Total reportable segments
Segment Reporting Information [Line Items]
Revenues									3,054.7	2,955.2	3,004.4
Operating Earnings									661.2	616.7	665.4
Depreciation & Amortization									52.8	42.9	39.5
Total Assets	2,079.1				1,967.9				2,079.1	1,967.9	1,745.7
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues									163.1	143.9	45.4
Operating Earnings									(48.9)	(31.2)	(52.7)
Depreciation & Amortization									7.4	4.9	1.0
Total Assets	$ 369.9				$ 296.2				$ 369.9	$ 296.2	$ 278.6