Fair Value Measurements and Derivative Instruments (Details) (Fair Value, Measurements, Nonrecurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Total
Assets:
Cash and cash equivalents	$ 204,687	$ 194,855
Total Assets	204,687	194,855
Liabilities:
Long-term debt (including current portion of long-term debt)	8,431,220	8,859,310
Total Liabilities	8,431,220	8,859,310
Level 1
Assets:
Cash and cash equivalents	204,367	194,855
Total Assets	204,367	194,855
Liabilities:
Long-term debt (including current portion of long-term debt)	2,888,255	3,917,398
Total Liabilities	2,888,255	3,917,398
Level 2
Assets:
Cash and cash equivalents	0	0
Total Assets	0	0
Liabilities:
Long-term debt (including current portion of long-term debt)	5,542,965	4,941,912
Total Liabilities	5,542,965	4,941,912
Level 3
Assets:
Cash and cash equivalents	0	0
Total Assets	0	0
Liabilities:
Long-term debt (including current portion of long-term debt)	0	0
Total Liabilities	0	0
Reported Value Measurement
Assets:
Cash and cash equivalents	204,687	194,855
Total Assets	204,687	194,855
Liabilities:
Long-term debt (including current portion of long-term debt)	8,074,804	8,489,947
Total Liabilities	$ 8,074,804	$ 8,489,947