Fair Value Measurements and Derivative Instruments (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Level 1
Assets:
Cash and cash equivalents	[1],[2]	$ 159,360	$ 189,241
Total Assets	[2]	159,360	189,241
Liabilities:
Long-term debt (including current portion of long-term debt)	[2],[3]	1,839,643	1,859,361
Total Liabilities	[2]	1,839,643	1,859,361
Level 2
Assets:
Cash and cash equivalents	[1]	0	0
Total Assets		0	0
Liabilities:
Long-term debt (including current portion of long-term debt)	[3]	7,239,250	6,902,053
Total Liabilities		7,239,250	6,902,053
Level 3
Assets:
Cash and cash equivalents	[1]	0	0
Total Assets		0	0
Liabilities:
Long-term debt (including current portion of long-term debt)	[3]	0	0
Total Liabilities		0	0
Total Carrying Amount
Assets:
Cash and cash equivalents	[1]	159,360	189,241
Total Assets		159,360	189,241
Liabilities:
Long-term debt (including current portion of long-term debt)	[3]	8,727,026	8,391,301
Total Liabilities		8,727,026	8,391,301
Total Fair Value
Assets:
Cash and cash equivalents	[1]	159,360	189,241
Total Assets		159,360	189,241
Liabilities:
Long-term debt (including current portion of long-term debt)	[3]	9,078,893	8,761,414
Total Liabilities		$ 9,078,893	$ 8,761,414

[1] Consists of cash and marketable securities with original maturities of less than 90 days.

[2] Inputs based on quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access. Valuation of these items does not entail a significant amount of judgment.

[3] Consists of unsecured revolving credit facilities, senior notes, senior debentures and term loans. Does not include our capital lease obligations.