Business Segments and Geographic Information - Segment Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 28, 2020	Mar. 30, 2019	Mar. 28, 2020	Mar. 30, 2019	Sep. 28, 2019
Segment Reporting Information [Line Items]
Total revenues	$ 756.1	$ 818.4	$ 1,606.6	$ 1,649.1
Income (loss) from operations	156.4	(323.2)	281.2	(182.7)
Depreciation and amortization	93.7	117.6	188.1	236.4
Capital expenditures	31.7	29.3	63.1	51.9
Identifiable assets	6,821.8		6,821.8		$ 6,442.1
Diagnostics
Segment Reporting Information [Line Items]
Total revenues	319.2	296.7	630.7	593.3
Income (loss) from operations	57.3	31.1	106.8	74.4
Depreciation and amortization	59.3	61.6	118.4	123.4
Capital expenditures	17.1	16.0	35.3	30.4
Identifiable assets	2,193.8		2,193.8		2,276.6
Breast Health
Segment Reporting Information [Line Items]
Total revenues	307.8	321.5	638.9	646.2
Income (loss) from operations	75.9	99.0	169.8	196.8
Depreciation and amortization	13.1	8.9	23.1	18.2
Capital expenditures	8.1	4.7	14.5	6.8
Identifiable assets	1,243.9		1,243.9		1,127.8
Medical Aesthetics
Segment Reporting Information [Line Items]
Total revenues	0.0	73.8	65.3	153.6
Income (loss) from operations	(2.4)	(473.9)	(53.4)	(499.1)
Depreciation and amortization	0.0	25.1	4.1	50.6
Capital expenditures	0.0	3.4	1.4	4.5
Identifiable assets	0.0		0.0		159.3
GYN Surgical
Segment Reporting Information [Line Items]
Total revenues	105.4	102.2	224.5	210.6
Income (loss) from operations	23.9	20.5	55.4	47.6
Depreciation and amortization	21.1	21.9	42.1	43.9
Capital expenditures	5.3	3.1	10.6	6.6
Identifiable assets	1,284.4		1,284.4		1,328.6
Skeletal Health
Segment Reporting Information [Line Items]
Total revenues	23.7	24.2	47.2	45.4
Income (loss) from operations	1.7	0.1	2.6	(2.4)
Depreciation and amortization	0.2	0.1	0.4	0.3
Capital expenditures	0.1	0.3	0.2	0.6
Identifiable assets	30.2		30.2		27.3
Corporate
Segment Reporting Information [Line Items]
Capital expenditures	1.1	$ 1.8	1.1	$ 3.0
Identifiable assets	$ 2,069.5		$ 2,069.5		$ 1,522.5