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Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Stock-Based Compensation) (Details) - USD ($) $ in Thousands		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 7,359	$ 7,891	$ 6,914
Income tax benefits		2,576	2,762	2,420
Excess tax benefits on settled share-based employee payments		$ 2,348	$ 1,597	$ 0
Federal statutory tax rate	21.00%	35.00%	35.00%	35.00%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		3 years
Shares granted during the year		57,746	58,610	58,302
Shares vested during the year		(57,473)	(52,385)	(60,379)
Unvested shares at end of year		106,053	109,806	106,091
Unrecognized compensation expense at end of year (in thousands)		$ 1,853	$ 1,853	$ 1,705
Total Shareholder Return Market-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year		114,390	116,435	116,435
Shares vested during the year		(107,649)	(111,665)	(171,334)
Shares earned based on market metrics		158,262	132,887	222,734
Unvested shares at end of year		218,507	222,228	223,697
Unrecognized compensation expense at end of year (in thousands)		$ 2,849	$ 3,409	$ 3,219
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted during the year		57,223	57,521	58,259
Shares vested during the year		(53,862)	(55,835)	0
Shares earned based on market metrics		41,502	90,460	0
Unvested shares at end of year		108,581	110,452	111,887
Unrecognized compensation expense at end of year (in thousands)		$ 1,856	$ 1,671	$ 1,840
Total Shareholder Return Market-Based Awards and Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		3 years
Dividend Component Liability, Current		$ 1,500	$ 1,500
Minimum [Member] | Total Shareholder Return Market-Based Awards and Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued range, percent of the performance shares granted		0.00%
Maximum [Member] | Total Shareholder Return Market-Based Awards and Performance Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock issued range, percent of the performance shares granted		200.00%

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