Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 147,778	$ 58,604
Adjustments to reconcile net income to net cash provided by operating activities:
Loss from discontinued operations	18	27
Depreciation and amortization	68,384	35,967
Compensation cost related to equity awards	10,749	3,948
Excess tax benefit from share-based compensation	(5,666)	(2,687)
Deferred income taxes	(18,802)	21,608
Net gain on sale of assets	(2,716)	(7,429)
Gain on insurance recoveries	0	(5,186)
Insurance proceeds received	10,353	21,373
Changes in assets and liabilities which provided (used) cash, net of effect of acquisitions:
Accounts receivable, net	(45,254)	3,617
Materials and supplies	(1,842)	(1,870)
Prepaid expenses and other	(2,111)	(2,331)
Accounts payable and accrued expenses	(13,412)	(35,365)
Other assets and liabilities, net	5,242	579
Net cash provided by operating activities from continuing operations	152,721	90,855
Net cash used in operating activities from discontinued operations	(18)	(27)
Net cash provided by operating activities	152,703	90,828
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(112,334)	(106,538)
Grant proceeds from outside parties	6,008	18,281
Cash paid for acquisitions, net of cash acquired	0	(837)
Proceeds from disposition of property and equipment	3,198	8,141
Net cash used in investing activities from continuing operations	(103,128)	(80,953)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on long-term borrowings, including capital leases	(267,961)	(131,390)
Proceeds from issuance of long-term debt	168,998	133,118
Debt amendment costs	(1,880)	0
Proceeds from employee stock purchases	9,177	10,742
Treasury stock purchases	(7,735)	(1,763)
Dividends paid on Series A-1 Preferred Stock	(2,139)	0
Excess tax benefit from share-based compensation	5,666	2,687
Net cash (used in)/provided by financing activities from continuing operations	(95,874)	13,394
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	64	(319)
(DECREASE)/INCREASE IN CASH AND CASH EQUIVALENTS	(46,235)	22,950
CASH AND CASH EQUIVALENTS, beginning of period	64,772	27,269
CASH AND CASH EQUIVALENTS, end of period	$ 18,537	$ 50,219