Financial Instruments - Fair Value of Interest Rate Derivatives by Balance Sheet Location (Details) (Interest Rate Contract [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	$ 0	$ 21,290
Not Designated as Hedging Instrument [Member] | Non-current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	0	5,134
Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	3,555	0
Not Designated as Hedging Instrument [Member] | Noncurrent Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Assets, at Fair Value	$ 81,762	$ 0