Summary of Significant Accounting Policies New Accounting Pronouncements and Changes in Accounting Principals (Details) - Adjustments for New Accounting Pronouncement [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Oct. 01, 2017	Oct. 01, 2017	Oct. 02, 2016	Dec. 31, 2018	Jan. 01, 2018	Jan. 01, 2017
ASU 2016-16 [Member] | Subsequent Event [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income tax benefit (expense)				$ (1.5)
ASU 2016-16 [Member] | Retained Earnings [Member] | Subsequent Event [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Estimated deferred tax assets					$ 30.0
ASU 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other income tax benefit (expense)	$ 0.3	$ 2.1
Excess tax benefit from stock-based compensation, Operating Activities			$ 2.3
Excess tax benefit from stock-based compensation, Financing Activities			$ 2.3
ASU 2016-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption						$ (0.2)