Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended		12 Months Ended
	Oct. 03, 2021	Jul. 04, 2021	Apr. 04, 2021	Sep. 27, 2020	Mar. 29, 2020	Oct. 03, 2021	Sep. 27, 2020	Jan. 03, 2021	Mar. 08, 2021	Nov. 18, 2020	Jan. 14, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill impairment charge	$ 0.0			$ 0.0	$ 147.7	$ 0.0	$ 147.7
Proceeds from Sale of Equity Securities, FV-NI						5.0
Brazil
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Indemnification liabilities, expense (income)						(0.1)
Insight
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional consideration payable											$ 1.6
Adjustment to earnout liability		$ 0.1						$ 0.1
Payment for contingent consideration liability	1.8
Greenwood/Asher
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional consideration payable										$ 2.1
Adjustment to earnout liability	2.4		$ (0.4)			2.0
Persol Holdings Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost of equity securities	18.6					18.6		20.1
Business Talent Group, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from Sale of Equity Securities, FV-NI		$ 5.0
Kenzie Academy Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities without readily determinable fair value, with changes in fair value in net income								1.4	$ 1.4
Debt and equity securities, realized gain (loss)			$ (1.4)
Other Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	6.5					6.5		5.1
Level 3 | Brazil
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Indemnification liability	2.5					2.5		2.6
Level 3 | Insight
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional consideration payable								1.7
Level 3 | Greenwood/Asher
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional consideration payable	4.1					4.1		$ 2.1
Level 3 | Other Long Term Liabilities | Greenwood/Asher
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional consideration payable	2.2					2.2
Level 3 | Accounts Payable and Accrued Liabilities | Greenwood/Asher
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Additional consideration payable	$ 1.9					$ 1.9