Consolidated Statements of Cash Flows (USD $)	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 173,375,000	$ 214,003,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	116,130,000	105,718,000
Compensation cost related to equity awards	9,063,000	13,620,000
Excess tax benefit from share-based compensation	(5,483,000)	(7,487,000)
Deferred income taxes	62,612,000	622,000
Net gain on sale of assets	(3,444,000)	(3,419,000)
Insurance proceeds received	5,527,000	10,353,000
Changes in assets and liabilities which provided/(used) cash, net of effect of acquisitions:
Accounts receivable, net	(32,222,000)	(42,607,000)
Materials and supplies	(1,070,000)	(1,105,000)
Prepaid expenses and other	5,568,000	(9,910,000)
Accounts payable and accrued expenses	34,990,000	(8,178,000)
Other assets and liabilities, net	3,957,000	7,073,000
Net cash provided by operating activities	369,003,000	278,683,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(271,696,000)	(170,435,000)
Grant proceeds from outside parties	43,518,000	23,878,000
Cash paid for acquisitions, net of cash acquired	(220,542,000)	0
Insurance proceeds for the replacement of assets	4,112,000	0
Proceeds from disposition of property and equipment	4,562,000	3,954,000
Net cash used in investing activities	(440,046,000)	(142,603,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Principal payments on long-term borrowings, including capital leases	(378,763,000)	(388,018,000)
Proceeds from issuance of long-term debt	398,761,000	215,443,000
Debt amendment costs	(3,880,000)	(1,880,000)
Proceeds from employee stock purchases	9,574,000	11,026,000
Treasury stock purchases	(4,062,000)	(10,941,000)
Dividends paid on Series A-1 Preferred Stock	0	(2,139,000)
Excess tax benefit from share-based compensation	5,483,000	7,487,000
Net cash provided by/(used in) financing activities	27,113,000	(169,022,000)
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	(154,000)	124,000
DECREASE IN CASH AND CASH EQUIVALENTS	(44,084,000)	(32,818,000)
CASH AND CASH EQUIVALENTS, beginning of period	62,876,000	64,772,000
CASH AND CASH EQUIVALENTS, end of period	$ 18,792,000	$ 31,954,000