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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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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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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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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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Number of shares issued during the period as a result of an employee stock purchase plan.

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Employee Stock Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Employee Stock Plans [Line Items]
Total pre-tax intrinsic value of options exercised	$ 31.0	$ 28.3	$ 25.6
Fair value	9.3	9.6	9.7
Grant date fair value	36.9	33.7	31.4
Shares vested during the year, fair value	43.9	36.9	29.8
Tax withholdings on vesting of equity awards	$ (14.5)	$ (11.6)	(10.7)
Purchase period (in months)	6 months
Maximum number of shares purchased (in shares)	7,000,000,000,000
Number of shares issued (in shares)	200,000	200,000
Shares issued, value	$ 16.9	$ 15.7
Employee Stock Option Plans
Employee Stock Plans [Line Items]
Unrecognized compensation expense related to outstanding stock awards	$ 19.4
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	1 year 10 months 24 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	$ 41.4
Weighted average period unrecognized compensation expense is expected to be recognized (in years)	1 year 9 months 18 days
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
Fifth Amended 2005 Plan \| Stock options
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Fifth Amended 2005 Plan \| Cash-settled stock appreciation rights
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Fifth Amended 2005 Plan \| Restricted Stock Units (RSUs)
Employee Stock Plans [Line Items]
Award vesting period (in years)	3 years
Fifth Amended 2005 Plan \| Performance units and performance options
Employee Stock Plans [Line Items]
Performance period	3 years
Employee Stock Purchase Plans
Employee Stock Plans [Line Items]
Number of shares available for issuance (in shares)	5,000,000.0
Total Varian Stockholders' Equity
Employee Stock Plans [Line Items]
Tax withholdings on vesting of equity awards	$ (14.5)	$ (11.6)	$ (10.7)
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 \| Fifth Amended 2005 Plan \| Restricted Stock Units (RSUs)
Employee Stock Plans [Line Items]
Award vesting period (in years)	1 year