Earnings (Loss) Per Common Unit (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings (Loss) Per Common Unit
Net income (loss) attributable to the Partnership	$ (74,085)	$ 140,312	$ 78,497	$ (84,029)	$ (54,109)	$ (27,151)	$ 60,217	$ 21,510	$ 60,695	$ 467	$ (118,668)
Less: Income allocable to phantom units									1,749	1,308	1,518
Income (loss) available for common unitholders									$ 58,946	$ (841)	$ (120,186)
Weighted average common units outstanding-basic (in units)									78,466	70,128	60,957
Effect of dilutive instruments (in units)									153
Weighted average common units outstanding-diluted (in units)									78,619	70,128	60,957
Net income (loss) attributable to the Partnership's common unitholders
Basic (in dollars per unit)	$ (0.87)	$ 1.77	$ 1.03	$ (1.13)	$ (0.76)	$ (0.39)	$ 0.84	$ 0.32	$ 0.75	$ (0.01)	$ (1.97)
Diluted (in dollars per unit)	$ (0.87)	$ 1.77	$ 1.03	$ (1.13)	$ (0.76)	$ (0.39)	$ 0.84	$ 0.32	$ 0.75	$ (0.01)	$ (1.97)
Anti-dilutive units (in units)										195