Quarterly report pursuant to Section 13 or 15(d)

Derivative Financial Instruments - Gain (Loss) on Derivatives (Details)

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Derivative Financial Instruments - Gain (Loss) on Derivatives (Details) - Interest rate swaps - USD ($)
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Cash flow hedges      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain (loss) recognized in OCI - effective portion $ 258,000 $ 93,000  
Interest Expense and Other | Cash flow hedges      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain (loss) recognized in income - effective portion 99,000 (21,000)  
Gain recognized in income - ineffective portion (16,000) $ (18,000)  
Other long-term liabilities | Level 2 | Derivative Financial Instruments | Recurring      
Derivative Instruments, Gain (Loss) [Line Items]      
Notional amount 75,000,000   $ 75,000,000
Derivative liability $ 1,529,000   $ 1,329,000