Commitments, Contingencies And Guarantees (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Payment Required Upon Termination Of Employment [Line Items]
Rent expense charged to operations	$ 23,000	$ 22,700	$ 20,500
Minimum royalty payments due through 2035	1,700
Total contingent liabilities	3,000	900
Purchase Obligation	11,800
Loss contingency, range of possible loss, maximum	2,500	2,600	3,500
Liabilities for indemnification obligations	0	0
Outstanding letters of credit to insurance company as security for workers' compensation claims	$ 1,000
Period for continued vesting of outstanding equity awards upon termination of CEO without cause other than following a change in control, years	two years
Payment Required To CEO Upon Termination Of Employment Without Cause Other Than Following Change In Control [Member]
Payment Required Upon Termination Of Employment [Line Items]
Employee agreement contingencies	$ 1,600
Payment Required To Officers Upon Termination Of Employment Following Change Of Control [Member]
Payment Required Upon Termination Of Employment [Line Items]
Employee agreement contingencies	29,400
Workers Compensation Insurance Policies [Member]
Payment Required Upon Termination Of Employment [Line Items]
Retained claim liability per incident	300	300	300
Employee Health Care Insurance Policy [Member]
Payment Required Upon Termination Of Employment [Line Items]
Retained claim liability per incident	1,000	450	430
General insurance expense	47,200	40,400	$ 34,600
Self Insurance Reserve	$ 4,200	$ 4,000