Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Asset Derivatives:
Gross amount of recognized assets	$ 2,128	$ 4,209
Gross amounts offset in the statement of financial position	(1,601)	(2,862)
Net amount	527	1,347
Liability Derivatives:
Gross amount of recognized liabilities	(4,331)	(4,287)
Gross amounts offset in the statement of financial position	1,601	2,862
Net amount	(2,730)	(1,425)
Total derivative instruments	$ (2,203)	$ (78)

Fair value of the gross assets less the gross liabilities of a derivative asset or group of derivative assets.

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Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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