Summary of Significant Accounting Policies (Accounting Pronouncements) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings		$ 1,206,723	$ 1,177,151
Net sales		1,436,499	1,230,754	$ 1,193,975
Pension Costs Guidance [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Curtailment gain		$ 7,217
Subsequent Event [Member] | Revenue Recognition Guidance [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Retained earnings	$ 4,000
Net sales	$ 15,000
Accounting Standards Update 2015-07 [Member] | New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Current deferred income tax assets			26,639
Current deferred income tax liabilities			$ 1,290