Summary Of Significant Accounting Policies (Reconciliation Of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 29, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jul. 01, 2018	Apr. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Basic EPS, Net Income	$ 1,556	$ (112,337)	$ (18,520)	$ (4,634)	$ (21,004)	$ (6,841)	$ 5,902	$ (17,441)	$ (133,935)	$ (39,384)	$ 11,789
Dilutive securities, principally common stock options, Net Income									0	0	0
Diluted EPS, Net Income									$ (133,935)	$ (39,384)	$ 11,789
Basic EPS, Shares									19,903	19,834	16,674
Dilutive securities, principally common stock options, Shares									0	0	175
Diluted EPS, Shares									19,903	19,834	16,849
Basic EPS, Per Share Amount	$ 0.08	$ (5.64)	$ (0.93)	$ (0.23)	$ (1.06)	$ (0.34)	$ 0.30	$ (0.88)	$ (6.73)	$ (1.99)	$ 0.71
Dilutive securities, principally common stock options, Per Share Amount									0	0	(0.01)
Diluted EPS, Per Share Amount	$ 0.08	$ (5.64)	$ (0.93)	$ (0.23)	$ (1.06)	$ (0.34)	$ 0.30	$ (0.88)	$ (6.73)	$ (1.99)	$ 0.70