Effect on Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Amount of gain (loss) recognized in OCI on derivatives
Amount of gain (loss) recognized in OCI on derivatives	$ (127)	$ (1,812)	$ (1,437)	$ (3,814)
Amount of gain (loss) reclassified from AOCI into income
Amount of gain (loss) reclassified from AOCI into income	(787)	(256)	(1,391)	(188)
Interest rate caps
Amount of gain (loss) recognized in OCI on derivatives
Amount of gain (loss) recognized in OCI on derivatives	(325)	(675)	(920)	(3,048)
Interest rate caps | Interest expense
Amount of gain (loss) reclassified from AOCI into income
Amount of gain (loss) reclassified from AOCI into income	(293)	(169)	(524)	(292)
Natural gas swaps
Amount of gain (loss) recognized in OCI on derivatives
Amount of gain (loss) recognized in OCI on derivatives	198	(1,137)	(517)	(766)
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	$ (494)	$ (87)	$ (867)	$ 104