CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest [Abstract]
Net income	$ 58,626	$ 21,388	$ 99,179	$ 41,788
Unrealized gain (loss) on defined benefit plan, net of tax	4,961	(16,570)	6,855	(6,851)
Unrealized (loss) gain on swaps and collars, net of tax	(2,027)	817	1,799	(621)
Unrealized foreign currency gain (loss), net of tax	12,849	6,733	9,111	(2,881)
Comprehensive income	74,409	12,368	116,944	31,435
Less: Comprehensive income attributable to noncontrolling interest	(3,252)	(355)	(4,353)	(587)
Total comprehensive income attributable to common stockholders	$ 71,157	$ 12,013	$ 112,591	$ 30,848