Condensed Consolidating Financial Information (Condensed Consolidating Statements of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net cash provided by (used in) operating activities	$ 1,653,942	$ 1,739,817	$ 1,642,585
Capital investments	(2,107,755)	(2,184,474)	(2,073,174)
Proceeds from sale of property and equipment	201,101	154,526	350,227
Transfers to restricted cash	(167,788)	(85,055)	(356,035)
Transfers from Restricted Cash	159,246	85,055	356,035
Other	8,519	5,158	(2,684)
Net cash used in investing activities	(1,906,677)	(2,024,790)	(1,725,631)
Payments on current portion of long-term debt	(1,200)	(1,200)	(1,200)
Payments on revolving long-term debt	(2,263,900)	(3,445,900)	(2,958,100)
Borrowings under revolving long-term debt	1,592,400	3,696,200	3,054,800
Proceeds from issuance of long-term debt	998,780
Other	(35,191)	35,203	(9,260)
Net cash provided by (used in) financing activities	290,889	284,303	86,240
Effect of exchange rate changes on cash	(198)	242	(323)
Increase (decrease) in cash and cash equivalents	37,956	(428)	2,871
Cash and cash equivalents at beginning of year	15,627	16,055	13,184
Cash and cash equivalents at end of year	53,583	15,627	16,055
Parent [Member]
Net cash provided by (used in) operating activities	(39,934)	14,688	25,865
Capital investments	(36,918)	(66,647)	(46,062)
Proceeds from sale of property and equipment	26,006
Transfers to restricted cash	(167,788)	(85,055)	(356,035)
Transfers from Restricted Cash	159,245	85,055	356,035
Other	(696)	16,263	11,864
Net cash used in investing activities	(20,151)	(50,384)	(34,198)
Intercompany activities	(198,023)	(242,277)	(76,904)
Payments on current portion of long-term debt	(1,200)	(1,200)	(1,200)
Payments on revolving long-term debt	(2,263,900)	(3,445,900)	(2,958,100)
Borrowings under revolving long-term debt	1,592,400	3,696,200	3,054,800
Proceeds from issuance of long-term debt	998,780
Other	(35,192)	35,203	(9,260)
Net cash provided by (used in) financing activities	92,865	42,026	9,336
Increase (decrease) in cash and cash equivalents	32,780	6,330	1,003
Cash and cash equivalents at beginning of year	14,711	8,381	7,378
Cash and cash equivalents at end of year	47,491	14,711	8,381
Guarantors [Member]
Net cash provided by (used in) operating activities	1,278,673	1,482,853	1,368,248
Capital investments	(1,868,487)	(1,916,246)	(1,718,847)
Proceeds from sale of property and equipment	169,149	154,261	348,274
Transfers from Restricted Cash	1
Other	(35,792)	(43,961)	(22,719)
Net cash used in investing activities	(1,735,129)	(1,805,946)	(1,393,292)
Intercompany activities	462,443	315,462	26,899
Other	1
Net cash provided by (used in) financing activities	462,444	315,462	26,899
Increase (decrease) in cash and cash equivalents	5,988	(7,631)	1,855
Cash and cash equivalents at beginning of year		7,631	5,776
Cash and cash equivalents at end of year	5,988		7,631
Non-Guarantors [Member]
Net cash provided by (used in) operating activities	415,203	242,276	248,472
Capital investments	(202,350)	(201,581)	(308,265)
Proceeds from sale of property and equipment	5,946	265	1,953
Other	45,007	32,856	8,171
Net cash used in investing activities	(151,397)	(168,460)	(298,141)
Intercompany activities	(264,420)	(73,185)	50,005
Net cash provided by (used in) financing activities	(264,420)	(73,185)	50,005
Effect of exchange rate changes on cash	(198)	242	(323)
Increase (decrease) in cash and cash equivalents	(812)	873	13
Cash and cash equivalents at beginning of year	916	43	30
Cash and cash equivalents at end of year	$ 104	$ 916	$ 43