Cash, Cash Equivalents And Marketable Securities (Summary Of The Amortized Costs And Fair Values Of Marketable Securities) (Details) - USD ($) $ in Thousands	Jul. 02, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
MARKETABLE SECURITIES, Amortized Cost	$ 128,743	$ 84,529
MARKETABLE SECURITIES, Fair Value	128,706	84,457
MARKETABLE SECURITIES, Gross Unrealized Gains	9	1
MARKETABLE SECURITIES, Gross Unrealized Losses	46	73
Tax-Exempt Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
MARKETABLE SECURITIES, Amortized Cost	25,020	38,223
MARKETABLE SECURITIES, Fair Value	24,983	38,151
MARKETABLE SECURITIES, Gross Unrealized Gains	9	1
MARKETABLE SECURITIES, Gross Unrealized Losses	46	73
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
MARKETABLE SECURITIES, Amortized Cost	103,723	46,306
MARKETABLE SECURITIES, Fair Value	$ 103,723	$ 46,306