Quarterly Financial Data (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Quarterly Financial Data
Revenue, net	$ 87,497	$ 25,847	$ 36,863	$ 57,189	$ 45,106	$ 73,831	$ 24,545	$ (2,787)	$ 207,396	$ 140,695	$ 268,581
Earnings (loss) before income taxes	635	(19,718)	(7,797)	7,667	(1,018)	9,877	(22,115)	(49,287)	(19,213)	(62,543)	(185,459)
Net earnings (loss) and comprehensive income (loss)	4,330	(13,409)	(7,845)	7,967	(1,277)	10,419	(15,397)	(37,346)	(8,957)	(43,601)	(165,772)
Earnings (loss) per unit	$ 0.12	$ (0.37)	$ (0.22)	$ 0.23	$ (0.02)	$ 0.15	$ (0.22)	$ (0.54)	$ (0.25)	$ (0.63)	$ (2.39)
Loss on extinguishment of debt	(36,697)								(36,697)	(599)	(4,861)
Write-down of inventory	$ 4,600							$ 22,281	$ 4,600	$ 22,281	$ 23,400