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Significant Accounting Policies - Fair Value Measurements (Details) - USD ($)
$ in Thousands
9 Months Ended
Sep. 24, 2017
Dec. 25, 2016
Measurement of financial assets and liabilities at fair value on a recurring basis    
Transfers among levels within the fair value hierarchy $ 0  
Carrying Value    
Measurement of financial assets and liabilities at fair value on a recurring basis    
Cash surrender value of life insurance policies 27,254 $ 21,690
Interest rate swap liabilities 2,454 770
Measured on Recurring Basis | Level 1    
Measurement of financial assets and liabilities at fair value on a recurring basis    
Cash surrender value of life insurance policies 27,254 21,690
Measured on Recurring Basis | Level 2    
Measurement of financial assets and liabilities at fair value on a recurring basis    
Interest rate swap liabilities $ 2,454 $ 770