Fair Value Measurements and Derivative Instruments (Details 2) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Total
Assets:
Derivative financial instruments	$ 96,489	$ 201,130
Investments	6,231	6,941
Total Assets	102,720	208,071
Liabilities:
Derivative financial instruments	85,119	84,344
Total Liabilities	85,119	84,344
Level 1
Assets:
Investments	6,231	6,941
Total Assets	6,231	6,941
Level 2
Assets:
Derivative financial instruments	96,489	201,130
Total Assets	96,489	201,130
Liabilities:
Derivative financial instruments	85,119	84,344
Total Liabilities	$ 85,119	$ 84,344

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

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Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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