Long-term Debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2012 7-5/8% Senior secured notes, due April 2019	Sep. 30, 2012 7-5/8% Senior secured notes, due April 2019	Mar. 31, 2011 7-5/8% Senior secured notes, due April 2019	Dec. 31, 2012 2.50% Convertible senior subordinated notes due February 2014	Sep. 30, 2012 2.50% Convertible senior subordinated notes due February 2014	Dec. 31, 2011 2.50% Convertible senior subordinated notes due February 2014	Dec. 31, 2012 8.75% Convertible senior subordinated notes due February 2016	Sep. 30, 2012 8.75% Convertible senior subordinated notes due February 2016
Long-term debt
Debt instrument, face amount	$ 504,900	$ 504,900				$ 55,077			$ 49,791
Long-term debt	101,271	100,539	400,000	400,000		51,970	51,278		49,301	49,261
Carrying amount of long-term debt, net of discounts	501,271	500,539
Interest rate on long-term debt (as a percent)			7.625%	7.625%	7.625%	2.50%	2.50%	2.50%	8.75%	8.75%
Face amount of note	$ 504,900	$ 504,900				$ 55,077			$ 49,791