CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net income (loss)	$ 13,935	$ (7,312)	$ 29,558	$ (14,498)
Pension and post-retirement obligations:
Amortization of actuarial losses and prior service cost to earnings, net of tax	335	1,026	671	2,052
Derivative instruments designated as cash flow hedges:
Change in fair value of derivatives, net of tax	(1,021)	(12,146)	(12,965)	(18,835)
Reclassification of realized loss (gain) to earnings, net of tax	3,135	(440)	4,743	(647)
Comprehensive income (loss)	16,384	(18,872)	22,007	(32,504)
Less: comprehensive income attributable to noncontrolling interest	95	75	171	154
Total comprehensive income (loss) attributable to common shareholders	$ 16,289	$ (18,947)	$ 21,836	(32,658)
ASU 2017-12
Derivative instruments designated as cash flow hedges:
Cumulative adjustment upon adoption of ASU 2017-12				$ (576)