Other Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Jan. 03, 2016	Sep. 05, 2017
Business Acquisition [Line Items]
Intangible amortization expense	$ 0.9	$ 0.6	$ 0.9
Long-term customer receivable	12.4
Teachers On Call, Inc.
Business Acquisition [Line Items]
Intangibles				$ 18.3
Finite-lived intangibles				$ 13.5
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
Finite-lived intangible assets, amortization expense, next 12 months	1.6
Finite-lived intangible assets, amortization expense, year 2	1.6
Finite-lived intangible assets, amortization expense, year 3	1.6
Finite-lived intangible assets, amortization expense, year 4	1.5
Finite-lived intangible assets, amortization expense, year 5	$ 1.2