Derivative Financial Instruments (Schedule of Offsetting of Derivative Assets) (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2017
Offsetting of Derivative Assets [Line Items]
Gross Amounts of Recognized Assets	$ 855	$ 1,799
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Of Assets Presented in the Condensed Consolidated Balance Sheets	855	1,799
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Financial Instruments	(837)	(1,799)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Cash Collateral Pledged	0	0
Net Amount	18	0
JP Morgan
Offsetting of Derivative Assets [Line Items]
Gross Amounts of Recognized Assets	28
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0
Net Amounts Of Assets Presented in the Condensed Consolidated Balance Sheets	28
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Financial Instruments	(10)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Cash Collateral Pledged	0
Net Amount	18
Bank of America
Offsetting of Derivative Assets [Line Items]
Gross Amounts of Recognized Assets	541	1,664
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Of Assets Presented in the Condensed Consolidated Balance Sheets	541	1,664
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Financial Instruments	(541)	(1,664)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Cash Collateral Pledged	0	0
Net Amount	0	0
Wells Fargo
Offsetting of Derivative Assets [Line Items]
Gross Amounts of Recognized Assets	286	135
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Of Assets Presented in the Condensed Consolidated Balance Sheets	286	135
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Financial Instruments	(286)	(135)
Gross Amounts Not Offset in the Condensed Consolidated Balance Sheets: Cash Collateral Pledged	0	0
Net Amount	$ 0	$ 0