Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Summary of Assets at Fair Value on a Recurring Basis (Details)

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Fair Value Measurements - Summary of Assets at Fair Value on a Recurring Basis (Details) - Recurring - USD ($)
$ in Thousands
Apr. 22, 2018
Dec. 31, 2017
Assets:    
Investments in rabbi trust $ 9,157 $ 9,292
Total assets measured at fair value 9,157 9,292
Level 1    
Assets:    
Investments in rabbi trust 9,157 9,292
Total assets measured at fair value 9,157 9,292
Level 2    
Assets:    
Investments in rabbi trust 0 0
Total assets measured at fair value 0 0
Level 3    
Assets:    
Investments in rabbi trust 0 0
Total assets measured at fair value $ 0 $ 0