Revenue - Business Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,347.0	$ 822.9	$ 756.1	$ 850.5	$ 865.8	$ 852.4	$ 818.4	$ 830.7	$ 3,776.4	$ 3,367.3	$ 3,217.9
United States
Disaggregation of Revenue [Line Items]
Revenues									2,863.2	2,536.0	2,417.6
International
Disaggregation of Revenue [Line Items]
Revenues									913.2	831.3	800.3
Diagnostics
Disaggregation of Revenue [Line Items]
Revenues									2,102.1	1,205.5	1,147.4
Diagnostics | United States
Disaggregation of Revenue [Line Items]
Revenues									1,582.4	921.3	881.6
Diagnostics | International
Disaggregation of Revenue [Line Items]
Revenues									519.7	284.2	265.8
Diagnostics | Cytology & Perinatal
Disaggregation of Revenue [Line Items]
Revenues									410.1	472.0	480.3
Diagnostics | Cytology & Perinatal | United States
Disaggregation of Revenue [Line Items]
Revenues									266.3	312.9	322.9
Diagnostics | Cytology & Perinatal | International
Disaggregation of Revenue [Line Items]
Revenues									143.8	159.1	157.4
Diagnostics | Molecular Diagnostics
Disaggregation of Revenue [Line Items]
Revenues									1,648.4	675.0	611.8
Diagnostics | Molecular Diagnostics | United States
Disaggregation of Revenue [Line Items]
Revenues									1,272.5	549.9	503.4
Diagnostics | Molecular Diagnostics | International
Disaggregation of Revenue [Line Items]
Revenues									375.9	125.1	108.4
Diagnostics | Blood Screening
Disaggregation of Revenue [Line Items]
Revenues									43.6	58.5	55.3
Diagnostics | Blood Screening | United States
Disaggregation of Revenue [Line Items]
Revenues									43.6	58.5	55.3
Diagnostics | Blood Screening | International
Disaggregation of Revenue [Line Items]
Revenues									0.0	0.0	0.0
Breast Health
Disaggregation of Revenue [Line Items]
Revenues									1,151.9	1,314.2	1,218.2
Breast Health | United States
Disaggregation of Revenue [Line Items]
Revenues									888.6	1,037.9	951.4
Breast Health | International
Disaggregation of Revenue [Line Items]
Revenues									263.3	276.3	266.8
Breast Health | Breast Imaging
Disaggregation of Revenue [Line Items]
Revenues									953.6	1,094.6	1,016.5
Breast Health | Breast Imaging | United States
Disaggregation of Revenue [Line Items]
Revenues									722.0	853.1	782.0
Breast Health | Breast Imaging | International
Disaggregation of Revenue [Line Items]
Revenues									231.6	241.5	234.5
Breast Health | Interventional Breast Solutions
Disaggregation of Revenue [Line Items]
Revenues									198.3	219.6	201.7
Breast Health | Interventional Breast Solutions | United States
Disaggregation of Revenue [Line Items]
Revenues									166.6	184.8	169.4
Breast Health | Interventional Breast Solutions | International
Disaggregation of Revenue [Line Items]
Revenues									31.7	34.8	32.3
Medical Aesthetics
Disaggregation of Revenue [Line Items]
Revenues									65.3	315.6	339.1
Medical Aesthetics | United States
Disaggregation of Revenue [Line Items]
Revenues									30.9	155.4	172.4
Medical Aesthetics | International
Disaggregation of Revenue [Line Items]
Revenues									34.4	160.2	166.7
Skeletal Health
Disaggregation of Revenue [Line Items]
Revenues									81.0	94.8	91.2
Skeletal Health | United States
Disaggregation of Revenue [Line Items]
Revenues									51.2	58.6	59.4
Skeletal Health | International
Disaggregation of Revenue [Line Items]
Revenues									$ 29.8	$ 36.2	$ 31.8