Derivative Financial Instruments (Schedule of Offsetting of Derivative Liabilities) (Details) - USD ($) $ in Thousands	Apr. 01, 2018	Dec. 31, 2017
Offsetting of Derivative Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	$ 3,433	$ 8,192
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Of Liabilities Presented in the Condensed Consolidated Balance Sheets	3,433	8,192
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	2,596	6,393
JP Morgan
Offsetting of Derivative Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	10
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0
Net Amounts Of Liabilities Presented in the Condensed Consolidated Balance Sheets	10
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	0
Bank of America
Offsetting of Derivative Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	2,500	7,815
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Of Liabilities Presented in the Condensed Consolidated Balance Sheets	2,500	7,815
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	1,959	6,151
Wells Fargo
Offsetting of Derivative Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	923	377
Gross Amounts Offset in the Condensed Consolidated Balance Sheets	0	0
Net Amounts Of Liabilities Presented in the Condensed Consolidated Balance Sheets	923	377
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	$ 637	$ 242