Segment Information - Operating Results Information for Each Reportable Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Apr. 03, 2015	Mar. 28, 2014	Apr. 03, 2015	Mar. 28, 2014
Segment Reporting Information [Line Items]
Revenues	$ 759,406	$ 778,506	$ 1,497,260	$ 1,490,008
Operating Earnings (Loss)	146,036	127,544	275,486	269,538
Operating Segments | Oncology Systems
Segment Reporting Information [Line Items]
Revenues	589,400	603,100	1,152,700	1,144,500
Operating Earnings (Loss)	125,900	124,900	252,000	245,800
Operating Segments | Imaging Components
Segment Reporting Information [Line Items]
Revenues	155,500	169,000	321,500	330,200
Operating Earnings (Loss)	40,000	42,200	81,200	82,900
Operating Segments | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	744,900	772,100	1,474,200	1,474,700
Operating Earnings (Loss)	165,900	167,100	333,200	328,700
Operating Segments | Other
Segment Reporting Information [Line Items]
Revenues	14,500	6,400	23,100	15,300
Operating Earnings (Loss)	(12,700)	(14,500)	(26,300)	(28,700)
Corporate
Segment Reporting Information [Line Items]
Operating Earnings (Loss)	$ (7,200)	$ (25,100)	$ (31,400)	$ (30,500)