Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Schedule of Fair Value Measured On Recurring Basis (Details)

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Fair Value Measurements - Schedule of Fair Value Measured On Recurring Basis (Details) - Recurring - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Fair value measurements    
Interest rate swap agreement - assets [1] $ 4,664 $ 8,521
Interest rate swap agreements - liabilities [2] (17,753) (16,948)
Total (13,089) (8,427)
Level 1    
Fair value measurements    
Interest rate swap agreement - assets [1] 0 0
Interest rate swap agreements - liabilities [2] 0 0
Total 0 0
Level 2    
Fair value measurements    
Interest rate swap agreement - assets [1] 4,664 8,521
Interest rate swap agreements - liabilities [2] (17,753) (16,948)
Total (13,089) (8,427)
Level 3    
Fair value measurements    
Interest rate swap agreement - assets [1] 0 0
Interest rate swap agreements - liabilities [2] 0 0
Total $ 0 $ 0
[1] Included in Other assets on the consolidated balance sheets
[2] Interest rate swap agreement liability values are included in current Other accrued liabilities or non-current Derivative financial instruments on the consolidated balance sheets depending on the maturity date of the swap.