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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Number of shares authorized for issuance under share-based payment arrangement.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Purchase price of common stock expressed as a percentage of its fair value.

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Employee Stock Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Oct. 02, 2020	Sep. 27, 2019	Sep. 28, 2018
Employee Stock Plans [Line Items]
Total pre-tax intrinsic value of options exercised	$ 42.3	$ 31.0	$ 28.3
Fair value	10.4	9.3	9.6
Grant date fair value	54.8	36.9	33.7
Shares vested during the year, fair value	40.9	43.9	36.9
Tax withholdings on vesting of equity awards	$ 12.8	$ 14.5	11.6
Purchase period (in months)	6 months
Maximum number of shares purchased (in shares)	7,000,000
Number of shares issued (in shares)	200,000	200,000
Shares issued, value	$ 18.7	$ 16.9
Number of shares available for issuance (in shares)	4,800,000
Stock options
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Cash-settled stock appreciation rights
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Unrecognized compensation expense related to outstanding stock awards	$ 1.9
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	2 years 1 month 6 days
Restricted Stock Units (RSUs)
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Performance units and performance options
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Employee Stock Option Plans
Employee Stock Plans [Line Items]
Unrecognized compensation expense related to outstanding stock awards	$ 15.4
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	1 year 9 months 18 days
Restricted Stock Restricted Stock Units Deferred Stock Units And Performance Units
Employee Stock Plans [Line Items]
Unrecognized compensation expense related to outstanding stock awards	$ 50.2
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	2 years
Employee Stock Purchase Plans
Employee Stock Plans [Line Items]
Common stock employee purchase price percentage lower than fair market value	85.00%
Fifth Amended 2005 Plan
Employee Stock Plans [Line Items]
Number of shares authorized (in shares)	31,000,000.0
Total Varian Stockholders' Equity
Employee Stock Plans [Line Items]
Tax withholdings on vesting of equity awards	$ 12.8	$ 14.5	$ 11.6
Common Stock
Employee Stock Plans [Line Items]
Shares withheld for employees minimum withholding taxes at vesting (in shares)	100,000	100,000	100,000
Tax withholdings on vesting of equity awards	$ 0.1	$ 0.1	$ 0.1
Director \| Restricted Stock Units (RSUs)
Employee Stock Plans [Line Items]
Award vesting period (in years)	1 year