Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 30, 2018
Persol Holdings Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cost of equity securities	$ 19.2	$ 18.8
Business Talent Group, LLC
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities without readily determinable fair value, amount	5.0	$ 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	1.3
Other Assets | Kenzie Academy Inc.
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity securities without readily determinable fair value, amount	$ 1.0