Fair Value Measurements and Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Assets:
Cash and cash equivalents	$ 241,237	$ 262,186	$ 451,460	$ 419,929
Fair Value, Measurements, Nonrecurring | Total
Assets:
Cash and cash equivalents	241,237	262,186
Total Assets	241,237	262,186
Liabilities:
Long-term debt (including current portion of long-term debt)	8,075,478	8,557,095
Total Liabilities	8,075,478	8,557,095
Fair Value, Measurements, Nonrecurring | Level 1
Assets:
Cash and cash equivalents	241,237	262,186
Total Assets	241,237	262,186
Liabilities:
Long-term debt (including current portion of long-term debt)	3,202,176	3,424,722
Total Liabilities	3,202,176	3,424,722
Fair Value, Measurements, Nonrecurring | Level 2
Liabilities:
Long-term debt (including current portion of long-term debt)	4,873,302	5,132,373
Total Liabilities	$ 4,873,302	$ 5,132,373