CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS
Net revenues	$ 280,819	$ 233,434	$ 518,289	$ 467,173
Material costs	89,271	69,972	164,441	147,213
Personnel costs	97,549	73,822	187,429	163,007
Other operating costs	32,721	8,277	64,181	44,163
General and administrative expenses	33,177	33,623	64,118	65,392
Depreciation and amortization	8,007	8,879	16,005	17,710
Income from operations	20,094	38,861	22,115	29,688
Interest expense, net	7,152	8,636	14,492	16,906
Non-service defined benefit plan expense	167	158	334	316
Income before income taxes	12,775	30,067	7,289	12,466
Provision (benefit) for income taxes	2,616	(987)	460	(2,840)
Net income	$ 10,159	$ 31,054	$ 6,829	$ 15,306
Basic and Diluted Per Common Share Data:
Basic income per share	$ 0.26	$ 0.82	$ 0.18	$ 0.41
Weighted average shares used to compute basic earnings per common share	38,647,042	37,958,408	38,458,733	37,749,930
Diluted income per share	$ 0.26	$ 0.81	$ 0.17	$ 0.40
Weighted average shares used to compute diluted earnings per common share	39,208,155	38,325,872	39,216,725	38,424,334