Segment Information (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment information
Derivative gain (loss)	$ 138	$ (6,753)	$ 7,506	$ (10,720)
Total revenue	459,628	518,366	926,958	1,030,842
Total segments
Segment information
Total segment revenue	486,058	528,577	968,389	1,046,514
Not allocated to segments
Segment information
Derivative gain (loss)	138	(6,753)	7,506	(10,720)
Adjustments for unconsolidated affiliates
Segment information
Total revenue	(33,016)	(3,833)	(60,547)	(3,833)
Reconciling adjustments
Segment information
Revenue deferral adjustment and other	$ 6,448	$ 375	$ 11,610	$ (1,119)