Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
OPERATING ACTIVITIES:
Net income	$ 11,057	$ 8,814
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	11,316	10,053
Deferred income taxes	3,285	1,389
(Gain) loss on sale of assets	(321)	106
Amortization of deferred financing fees	317	403
Share-based compensation expense	552	1,766
Changes in assets and liabilities:
Accounts receivable	45,791	(26,742)
Contract revenues in excess of billings	(34,691)	3,188
Inventories	(5,703)	(3,379)
Prepaid expenses and other current assets	(6,612)	(832)
Accounts payable and accrued expenses	12,247	(10,303)
Billings in excess of contract revenues	(11,126)	6,055
Other noncurrent assets and liabilities	205	242
Cash (used in) provided by operating activities	26,317	(9,240)
INVESTING ACTIVITIES:
Purchases of property and equipment	(28,866)	(27,038)
Proceeds from dispositions of property and equipment	1,110
Cash used in investing activities	(27,756)	(27,038)
FINANCING ACTIVITIES:
Taxes paid on settlement of vested share awards	(1,827)	(3,784)
Exercise of options and purchases from employee stock plans	390	1,260
Cash used in financing activities	(1,437)	(2,524)
Net (decrease) increase in cash, cash equivalents and restricted cash	(2,876)	(38,802)
Cash, cash equivalents and restricted cash at beginning of period	147,459	216,510
Cash, cash equivalents and restricted cash at end of period	144,583	177,708
Cash and cash equivalents	142,583	177,708
Restricted cash included in other long-term assets	2,000
Supplemental Cash Flow Information
Cash paid for interest	100	106
Cash paid for income taxes	58	58
Non-cash Investing and Financing Activities
Property and equipment purchased but not yet paid	$ 10,319	$ 5,855