Financial Instruments and Concentrations of Risk (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Schedule of Changes in Fair Value of Financial Assets (Liabilities) Classified as Level 3
Net assets (liabilities)—beginning balance	$ 0		$ (17,739)		$ (40,347)
Transfers out of Level 3	0	[1]	8,515	[1]	4,072	[1]
Total realized and unrealized gain (loss) included in earnings	0	[2]	11,041	[2]	(5,634)	[2]
Settlements	0		(1,817)		24,170
Net assets (liabilities)—ending balance	0		0		(17,739)
Amount of total gain or loss included in earnings for the period attributable to the change in unrealized gain or loss relating to assets and liabilities still held at the reporting date	0		0		(830)
Commodity Derivatives [Member]
Schedule of Changes in Fair Value of Financial Assets (Liabilities) Classified as Level 3
Net assets (liabilities)—beginning balance	0		(547)		(23,438)
Transfers out of Level 3	0	[1]	(419)	[1]	4,072	[1]
Total realized and unrealized gain (loss) included in earnings	0	[2]	2,783	[2]	(5,351)	[2]
Settlements	0		(1,817)		24,170
Net assets (liabilities)—ending balance	0		0		(547)
Amount of total gain or loss included in earnings for the period attributable to the change in unrealized gain or loss relating to assets and liabilities still held at the reporting date	0		0		(547)
Warrants [Member]
Schedule of Changes in Fair Value of Financial Assets (Liabilities) Classified as Level 3
Net assets (liabilities)—beginning balance	0		(17,192)		(16,909)
Transfers out of Level 3	0	[1]	8,934	[1]	0	[1]
Total realized and unrealized gain (loss) included in earnings	0	[2]	8,258	[2]	(283)	[2]
Settlements	0		0		0
Net assets (liabilities)—ending balance	0		0		(17,192)
Amount of total gain or loss included in earnings for the period attributable to the change in unrealized gain or loss relating to assets and liabilities still held at the reporting date	$ 0		$ 0		$ (283)

[1] In these tables, transfers in and transfers out are recognized as of the beginning of the reporting period for commodity derivatives and as of the transfer date for warrants.

[2] Gains and losses related to commodity derivatives are reported in product revenue. Gains and losses related to warrants are recorded in other expense (income).