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
Mar. 31, 2018
Dec. 31, 2017
Fair value measurements    
Interest rate swap agreements - assets [1] $ 13,833 $ 7,058
Interest rate swap agreements - liabilities [2] (6,553) (13,817)
Total 7,280 (6,759)
Level 1    
Fair value measurements    
Interest rate swap agreements - assets [1] 0 0
Interest rate swap agreements - liabilities [2] 0 0
Total 0 0
Level 2    
Fair value measurements    
Interest rate swap agreements - assets [1] 13,833 7,058
Interest rate swap agreements - liabilities [2] (6,553) (13,817)
Total 7,280 (6,759)
Level 3    
Fair value measurements    
Interest rate swap agreements - assets [1] 0 0
Interest rate swap agreements - liabilities [2] 0 0
Total $ 0 $ 0
[1] Included in non-current Other assets on the condensed consolidated balance sheets
[2] Included in non-current Derivative financial instruments on the condensed consolidated balance sheets.