Quarterly report pursuant to Section 13 or 15(d)

Fair Value Disclosures - Financial Assets and Liabilities Measured at Fair Value (Details)

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Fair Value Disclosures - Financial Assets and Liabilities Measured at Fair Value (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps $ 132 $ 0
Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps 0 0
Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps 132 0
Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps 0 0
Supplemental Employee Retirement Plan [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
SERP 1,945 1,858
Supplemental Employee Retirement Plan [Member] | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
SERP 0 0
Supplemental Employee Retirement Plan [Member] | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
SERP 1,945 1,858
Supplemental Employee Retirement Plan [Member] | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
SERP 0 0
Interest Rate Swap [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps 13,616 9,419
Interest Rate Swap [Member] | Level 1    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps 0 0
Interest Rate Swap [Member] | Level 2    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps 13,616 9,419
Interest Rate Swap [Member] | Level 3    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Interest rate swaps $ 0 $ 0