Derivative Financial Instruments - Changes in Fair Value of Derivative Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax:
Net loss (gain) recognized in other comprehensive loss	$ (1,389)	$ 526	$ 3,492	$ 8,740
Gain recognized in earnings	900	(400)	1,500	(700)
Interest rate swap agreements
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax:
Gain recognized in earnings	(35)	(37)	(70)	(74)
Derivative contracts
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax:
Beginning balance	11,301	17,415	15,989	9,238
Loss (gain) recognized in other comprehensive loss	1,880	928	(2,284)	9,284
Amounts reclassified from other comprehensive loss to earnings	(495)	(425)	(984)	(567)
Net loss (gain) recognized in other comprehensive loss	1,385	503	(3,268)	8,717
Ending balance	$ 12,651	$ 17,881	$ 12,651	$ 17,881