Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating Activities:
Net income	$ 37,676	$ 43,629
Noncash items included in net income:
Depreciation and amortization	56,910	48,525
Other, net	8,908	5,538
Changes in operating assets and liabilities, net	14,165	16,346
Net cash provided by operating activities	117,659	114,038
Investing Activities:
Acquisition of business, net of cash received		(22,238)
Acquisition of property and equipment	(108,871)	(68,835)
Proceeds from disposal of property and equipment	1,046	665
Net cash used in investing activities	(107,825)	(90,408)
Financing Activities:
Repayment of revolving credit agreement	(143,298)	(217,906)
Borrowing of revolving credit agreement	143,263	197,906
Proceeds from stock option exercises (including excess tax benefits)	248	2,816
Repayment of senior notes	(3,571)	(3,571)
Repayment of capital leases	(5,811)	(2,247)
Other financing activity		(455)
Net cash used in financing activities	(9,169)	(23,457)
Net Increase in Cash and Cash Equivalents	665	173
Cash and cash equivalents, beginning of period	124	4,367
Cash and cash equivalents, end of period	789	4,540
Non Cash Investing Activities
Equipment financed with capital leases	$ 34,683	$ 23,979