Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating Activities:
Net income	$ 22,259	$ 21,125
Noncash items included in net income:
Depreciation and amortization	26,782	23,030
Other, net	8,076	3,608
Changes in operating assets and liabilities, net	(26,717)	(12,261)
Net cash provided by operating activities	30,400	35,502
Investing Activities:
Acquisition of property and equipment	(56,741)	(46,881)
Proceeds from disposal of property and equipment	275	100
Net cash used in investing activities	(56,466)	(46,781)
Financing Activities:
Repayment of revolving credit agreement	(55,780)	(42,718)
Borrowing of revolving credit agreement	86,388	50,550
Proceeds from stock option exercises	1,798	4,018
Shares withheld for taxes	(3,268)	(1,302)
Debt issuance costs	(646)
Repayment of finance leases	(4,589)	(3,493)
Net cash provided by financing activities	23,903	7,055
Net Decrease in Cash and Cash Equivalents	(2,163)	(4,224)
Cash and cash equivalents, beginning of period	2,194	4,720
Cash and cash equivalents, end of period	$ 31	496
Non Cash Investing Activities
Equipment financed with finance leases		$ 5,318