Consolidated Statements of Cash Flows (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income (loss)	$ (21,574,000)	$ 34,368,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	101,848,000	89,520,000
Accretion on asset retirement obligation	55,000	56,000
Change in allowance for doubtful accounts	224,000	447,000
Amortization of deferred financing costs	1,512,000	1,392,000
Amortization and retirement of discount or premium on notes	(108,000)	(102,000)
Non-cash compensation	6,129,000	5,821,000
Loss on disposal of assets	1,879,000	2,699,000
Deferred income taxes	(10,755,000)	19,949,000
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable	(18,346,000)	16,180,000
Inventories	158,000	(4,831,000)
Prepaid expenses and other current assets	(2,730,000)	(1,048,000)
Other assets	229,000	1,237,000
Accounts payable	(4,874,000)	(2,049,000)
Income tax receivable	(791,000)	(1,306,000)
Other liabilities	2,395,000	3,297,000
Accrued expenses	13,118,000	11,909,000
Net cash provided by operating activities	68,369,000	177,539,000
Cash flows from investing activities:
Purchase of property and equipment	(77,599,000)	(86,733,000)
Proceeds from sale of mutual fund	5,635,000
Proceeds from sale of assets	7,658,000	4,219,000
Payments for other long-term assets	(569,000)	(351,000)
Payments for businesses, net of cash acquired	(16,463,000)	(41,769,000)
Net cash used in investing activities	(81,338,000)	(124,634,000)
Cash flows from financing activities:
Payments of debt	(22,632,000)	(19,866,000)
Purchase of treasury stock	(3,528,000)	(8,472,000)
Tax withholding from exercise of stock options	(154,000)	(128,000)
Exercise of employee stock options	456,000	794,000
Deferred loan costs and other financing activities	(119,000)	(142,000)
Net cash used in financing activities	(25,977,000)	(27,814,000)
Net (decrease) increase in cash and equivalents	(38,946,000)	25,091,000
Cash and cash equivalents - beginning of period	134,565,000	78,458,000
Cash and cash equivalents - end of period	$ 95,619,000	$ 103,549,000