Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value	$ 47,720
Quoted Prices In Active Markets for Identical Assets [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value	0
Quoted Prices In Active Markets for Identical Assets [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value	5,551
Significant Other Observable Inputs [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value	47,720
Significant Other Observable Inputs [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value	0
Significant Unobservable Inputs [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value	0
Significant Unobservable Inputs [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value	0
Recurring [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value, Total	53,271	20,261
Liabilities, Fair Value Disclosure [Abstract]
Liabilities, Fair Value, Total	(11,937)	(35,750)
Recurring [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value		12,955
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liabilities, Fair Value	(11,937)	(35,750)
Recurring [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value	5,551	7,306
Recurring [Member] \| Quoted Prices In Active Markets for Identical Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value, Total	5,551	7,306
Liabilities, Fair Value Disclosure [Abstract]
Liabilities, Fair Value, Total	0	0
Recurring [Member] \| Quoted Prices In Active Markets for Identical Assets [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value		0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liabilities, Fair Value	0	0
Recurring [Member] \| Quoted Prices In Active Markets for Identical Assets [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value		7,306
Recurring [Member] \| Significant Other Observable Inputs [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value, Total	47,720	12,955
Liabilities, Fair Value Disclosure [Abstract]
Liabilities, Fair Value, Total	(11,937)	(35,750)
Recurring [Member] \| Significant Other Observable Inputs [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value		12,955
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liabilities, Fair Value	(11,937)	(35,750)
Recurring [Member] \| Significant Other Observable Inputs [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value		0
Recurring [Member] \| Significant Unobservable Inputs [Member]
Assets, Fair Value Disclosure [Abstract]
Assets, Fair Value, Total	0	0
Liabilities, Fair Value Disclosure [Abstract]
Liabilities, Fair Value, Total	0	0
Recurring [Member] \| Significant Unobservable Inputs [Member] \| Hedging contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Assets, Fair Value		0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liabilities, Fair Value	0	0
Recurring [Member] \| Significant Unobservable Inputs [Member] \| Money market funds [Member]
Assets, Fair Value Disclosure [Abstract]
Cash and Cash Equivalents, Fair Value		$ 0

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 includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

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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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- Definition

Fair values as of the balance sheet date of all liabilities 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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