Revenue Recognition (Extended Warranties and Post-Contract Support) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Deferred revenue	$ 101,987	$ 110,158
Extended warranties and post contract support
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Post-contract support contract, term	12 months
Deferred revenue	$ 40,700	$ 40,300
Deferred revenue recognized	18,800
Estimation of future revenues	$ 27,700
Extended warranties and post contract support | Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Extended product warranty, term	1 year
Extended warranties and post contract support | Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Extended product warranty, term	5 years