Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities:
Net income	$ 43,397	$ 37,676
Noncash items included in net income:
Depreciation and amortization	64,607	56,910
Other, net	18,812	8,908
Changes in operating assets and liabilities, net	921	14,815
Net cash provided by operating activities	127,737	118,309
Investing Activities:
Acquisition of property and equipment	(155,676)	(108,871)
Proceeds from disposal of property and equipment	3,090	1,046
Net cash used in investing activities	(152,586)	(107,825)
Financing Activities:
Repayment of revolving credit agreement	(159,102)	(143,298)
Borrowing of revolving credit agreement	193,601	143,263
Proceeds from stock option exercises	2,531	248
Shares withheld for taxes	(1,249)	(650)
Repayment of senior notes	(3,571)	(3,571)
Repayment of capital leases	(8,819)	(5,811)
Net cash provided by (used in) financing activities	23,391	(9,819)
Net Increase (Decrease) in Cash and Cash Equivalents	(1,458)	665
Cash and cash equivalents, beginning of period	1,539	124
Cash and cash equivalents, end of period	81	789
Non Cash Investing Activities
Equipment financed with capital leases	$ 31,320	$ 34,683