Fair Value Measurements and Derivative Instruments (Details 2) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Total
Assets:
Derivative financial instruments	$ 81,561	$ 96,489
Investments	6,255	6,231
Total Assets	87,816	102,720
Liabilities:
Derivative financial instruments	141,307	85,119
Total Liabilities	141,307	85,119
Level 1
Assets:
Investments	6,255	6,231
Total Assets	6,255	6,231
Level 2
Assets:
Derivative financial instruments	81,561	96,489
Total Assets	81,561	96,489
Liabilities:
Derivative financial instruments	141,307	85,119
Total Liabilities	$ 141,307	$ 85,119

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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