Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Effect on Other Comprehensive Income (Details)

v3.10.0.1
Financial Instruments - Effect on Other Comprehensive Income (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Amount of gain (loss) recognized in OCI on derivatives        
Amount of gain (loss) recognized in OCI on derivatives $ 393 $ (1,870) $ 3,878 $ (5,499)
Amount of gain (loss) reclassified from AOCI into income        
Amount of gain (loss) reclassified from AOCI into income (101) (107) (265) (126)
Interest rate caps        
Amount of gain (loss) recognized in OCI on derivatives        
Amount of gain (loss) recognized in OCI on derivatives 93 (1,842) 3,396 (4,712)
Interest rate caps | Interest expense        
Amount of gain (loss) reclassified from AOCI into income        
Amount of gain (loss) reclassified from AOCI into income (71) (13) (164) (22)
Natural gas swaps        
Amount of gain (loss) recognized in OCI on derivatives        
Amount of gain (loss) recognized in OCI on derivatives 300 (28) 482 (787)
Natural gas swaps | Cost of goods sold        
Amount of gain (loss) reclassified from AOCI into income        
Amount of gain (loss) reclassified from AOCI into income $ (30) $ (94) $ (101) $ (104)