Guarantor Financial Information (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Condensed consolidating financial statements
Current assets	$ 124,470	$ 142,943
Property and equipment, net	1,420,358	1,067,551
Investments in subsidiaries	0	0
Fair value of derivatives	4,236	0
Other assets	25,520	15,777
TOTAL ASSETS	1,574,584	1,226,271	890,917
Current liabilities	120,914	156,230
Non-current liabilities:
Long-term debt	809,585	529,535
Fair value of derivatives	0	494
Deferred income taxes	155,830	134,209
Other	109,639	62,302
TOTAL NON-CURRENT LIABILITIES	1,075,054	726,540
Equity	378,616	343,501	249,452	212,275
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	1,574,584	1,226,271
Issuer
Condensed consolidating financial statements
Current assets	133,080	142,102
Property and equipment, net	1,053,453	737,562
Investments in subsidiaries	305,899	271,342
Fair value of derivatives	4,236
Other assets	12,112	13,538
TOTAL ASSETS	1,508,780	1,164,544
Current liabilities	241,200	233,729
Non-current liabilities:
Long-term debt	809,585	529,535
Fair value of derivatives		494
Deferred income taxes	143,699	141,923
Other	41,499	34,738
TOTAL NON-CURRENT LIABILITIES	994,783	706,690
Equity	272,797	224,125
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	1,508,780	1,164,544
Guarantor Subsidiaries
Condensed consolidating financial statements
Current assets	224,210	164,515
Property and equipment, net	366,905	329,989
Investments in subsidiaries	0	0
Fair value of derivatives	0
Other assets	13,408	2,239
TOTAL ASSETS	604,523	496,743
Current liabilities	112,534	86,175
Non-current liabilities:
Long-term debt	0	0
Fair value of derivatives		0
Deferred income taxes	117,950	111,662
Other	68,140	27,564
TOTAL NON-CURRENT LIABILITIES	186,090	139,226
Equity	305,899	271,342
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	604,523	496,743
Adjustments/Eliminations
Condensed consolidating financial statements
Current assets	(232,820)	(163,674)
Property and equipment, net	0	0
Investments in subsidiaries	(305,899)	(271,342)
Fair value of derivatives	0
Other assets	0	0
TOTAL ASSETS	(538,719)	(435,016)
Current liabilities	(232,820)	(163,674)
Non-current liabilities:
Long-term debt	0	0
Fair value of derivatives		0
Deferred income taxes	(105,819)	(119,376)
Other	0	0
TOTAL NON-CURRENT LIABILITIES	(105,819)	(119,376)
Equity	(200,080)	(151,966)
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ (538,719)	$ (435,016)