Derivative Financial Instruments - Changes in Fair Value of Derivative Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax:
Net (gain) loss recognized in other comprehensive income/loss	$ (573)	$ 2,456	$ 8,167	$ 8,123
Gain recognized in earnings	(1,500)	500	(2,200)	1,600
Derivative contracts
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax:
Beginning balance	17,881	9,146	9,238	3,548
(Gain) loss recognized in other comprehensive income/loss	(72)	2,472	9,212	8,062
Amounts reclassified from other comprehensive loss to earnings	(501)	(28)	(1,068)	75
Net (gain) loss recognized in other comprehensive income/loss	(573)	2,444	8,144	8,137
Ending balance	17,272	11,542	17,272	11,542
Interest rate swap agreements
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax:
Gain recognized in earnings	$ (36)	$ (48)	$ (110)	$ (143)