Stockholders' Equity - Changes in Accumulated Other Comprehensive Income by Component, Net of Tax (Details) - USD ($) $ in Millions		12 Months Ended
	Mar. 01, 2022	Dec. 29, 2024	Dec. 31, 2023	Jan. 01, 2023
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of year		$ 1,253.7	$ 1,254.2
Balance at end of year		1,234.6	1,253.7	$ 1,254.2
Other Expense
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income (loss)				(1.4)
Gain (Loss) on Disposal of Assets
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income (loss)				1.4
PersolKelly Pte. Ltd.
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income (loss)	$ 1.9
Foreign currency translation adjustments:
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of year		0.6	(7.4)	(25.0)
Other comprehensive income (loss) before classifications		(6.9)	8.0	(7.5)
Net current-period other comprehensive income (loss)		(7.5)	8.0	17.6
Balance at end of year		(6.9)	0.6	(7.4)
Foreign currency translation adjustments: | Liquidation of Subsidiary
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income (loss)		0.0	0.0	20.4
Foreign currency translation adjustments: | Equity Method Investment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income (loss)		(0.6)	0.0	4.7
Foreign currency translation adjustments: | PersolKelly Pte. Ltd. | Other Expense
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive income (loss)				(1.9)
Pension liability adjustments:
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of year		(0.4)	(1.1)	(2.7)
Other comprehensive income (loss) before classifications		0.0	0.6	1.5
Amounts reclassified from accumulated other comprehensive income (loss)		0.4	0.1	0.1
Net current-period other comprehensive income (loss)		0.4	0.7	1.6
Balance at end of year		0.0	(0.4)	(1.1)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of year		0.2	(8.5)	(27.7)
Balance at end of year		$ (6.9)	$ 0.2	$ (8.5)