Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
CURRENT ASSETS: [Abstract]
Cash and cash equivalents	$ 27,269	$ 27,417
Accounts receivable, net	165,768	132,225
Materials and supplies	14,445	13,259
Prepaid expenses and other	13,332	14,529
Deferred income tax assets, net	19,385	21,518
Total current assets	240,199	208,948
PROPERTY AND EQUIPMENT, net	1,643,589	1,444,177
GOODWILL	160,277	160,629
INTANGIBLE ASSETS, net	230,628	237,355
DEFERRED INCOME TAX ASSETS, net	2,342	2,879
OTHER ASSETS, net	17,122	13,572
Total assets	2,294,157	2,067,560
CURRENT LIABILITIES: [Abstract]
Current portion of long-term debt	57,168	103,690
Accounts payable	134,081	124,948
Accrued expenses	69,097	76,248
Deferred income tax liabilities, net	925
Total current liabilities	261,271	304,886
LONG-TERM DEBT, less current portion	569,026	475,174
DEFERRED INCOME TAX LIABILITIES, net	285,780	263,361
DEFERRED ITEMS - grants from outside parties	198,824	183,356
OTHER LONG-TERM LIABILITIES	18,622	23,543
COMMITMENTS AND CONTINGENCIES	0	0
STOCKHOLDERS' EQUITY: [Abstract]
Additional paid-in capital	385,473	358,024
Retained earnings	741,669	622,185
Accumulated other comprehensive income	37,895	40,114
Treasury stock, at cost	204,952	203,626
Total stockholders' equity	960,634	817,240
Total liabilities and stockholders' equity	2,294,157	2,067,560
Class A [Member]
STOCKHOLDERS' EQUITY: [Abstract]
Common Stock	527	519
Class B [Member]
STOCKHOLDERS' EQUITY: [Abstract]
Common Stock	$ 22	$ 24