Goodwill - Changes in the Net Carrying Amount of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 30, 2025	Jun. 29, 2025	Dec. 29, 2024
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 304.2	$ 304.2	$ 151.1
Additions			225.9
Impairment adjustments			(72.8)
Adjustments		(0.1)
Reallocation		0.0
Goodwill, ending balance		304.1	304.2
Science, Engineering & Technology
Goodwill [Roll Forward]
Goodwill, beginning balance	261.4	261.4	111.3
Additions			222.9
Impairment adjustments			(72.8)
Adjustments		0.0
Reallocation		(22.3)
Goodwill, ending balance		239.1	261.4
Education
Goodwill [Roll Forward]
Goodwill, beginning balance	42.8	42.8	39.8
Additions			3.0
Impairment adjustments			0.0
Adjustments		(0.1)
Reallocation		0.0
Goodwill, ending balance		42.7	42.8
Enterprise Talent Management
Goodwill [Roll Forward]
Goodwill, beginning balance	0.0	0.0	0.0
Additions			0.0
Impairment adjustments			0.0
Adjustments		0.0
Reallocation	$ 22.3	22.3
Goodwill, ending balance		$ 22.3	$ 0.0

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

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+ Details

- Definition

Amount of impairment loss from asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

+ References + Details

KELLY SERVICES INC 10-Q