Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Operating Activities:
Net income	$ 79,424	$ 37,291
Noncash items included in net income:
Depreciation and amortization	39,952	35,372
Deferred income taxes	(2,030)	1,327
Other, net	181	2,365
Changes in operating assets and liabilities, net	(21,566)	(15,384)
Net cash provided by operating activities	95,961	60,971
Investing Activities:
Acquisition of property and equipment	(46,259)	(25,568)
Proceeds from disposal of property and equipment	883	180
Net cash used in investing activities	(45,376)	(25,388)
Financing Activities:
Repayments of revolving credit agreement		(7,713)
Borrowings of revolving credit agreement		7,713
Proceeds from stock option exercises	907	3,678
Shares withheld for taxes	(11,230)	(6,350)
Repayment of finance leases	(5,525)	(4,959)
Net cash used in financing activities	(15,848)	(7,631)
Net Increase in Cash and Cash Equivalents	34,737	27,952
Cash and Cash Equivalents, beginning of period	106,588	25,308
Cash and Cash Equivalents, end of period	$ 141,325	$ 53,260