Income Taxes - Deferred Taxes (Details) - USD ($) $ in Millions	Dec. 30, 2018	Dec. 31, 2017
Deferred tax assets:
Allowance for doubtful accounts	$ 0.6	$ 0.2
Sundry accruals	1.1	1.5
Vacation accrual	2.7	3.2
Stock-based compensation	4.2	3.1
Payroll related accruals	2.4	2.1
Lease accruals	2.0	2.5
Investments	1.3	1.3
Net operating loss carryforwards	81.7	95.7
Capital loss carryforwards	0.0	1.9
Tax credit carryforwards	9.9	9.5
Deferred revenue	1.5	1.9
Reserves and other	10.8	6.1
Gross deferred tax assets	120.1	127.1
Valuation allowance	(92.2)	(87.5)
Total deferred tax assets, net of valuation allowance	27.9	39.6
Deferred tax liabilities:
Unearned revenue	(23.9)	(38.8)
Other intangibles	(8.9)	(5.4)
Property and equipment, principally due to differences in depreciation	(0.9)	(0.7)
Other	(1.2)	(1.7)
Total deferred tax liabilities	(34.9)	(46.6)
Net deferred tax liability	$ (7.0)	$ (7.0)