Summarized Quarterly Financial Information - Unaudited (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	2 Months Ended		3 Months Ended								4 Months Ended		12 Months Ended
	Dec. 31, 2012		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012		Mar. 31, 2012		Oct. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 38,186		$ 53,172	$ 55,587	$ 38,102	$ 36,009	$ 33,413		$ 36,041		$ 33,951		$ 182,870	$ 141,591	$ 160,700
Income (Loss) from operations	(24,027)	[1]	4,370	1,687	4,109	4,236	(52,183)	[1]	(18,314)	[1]	(35,919)	[1]	14,402	(130,443)	8,738
Income (loss) available to common stockholders	(25,451)	[1]	2,291	383	3,662	2,607	(54,520)	[1]	(18,608)	[1]	(38,639)	[1]	8,943	(137,218)	5,409
Earnings per share, Basic (in usd per share)	$ (0.41)		$ 0.04	$ 0.01	$ 0.06	$ 0.04	$ (0.87)		$ (0.30)		$ (0.62)		$ 0.14	$ (2.20)	$ 0.08
Earnings per share, Diluted (in usd per share)	$ (0.41)		$ 0.04	$ 0.01	$ 0.06	$ 0.04	$ (0.87)		$ (0.30)		$ (0.62)		$ 0.14	$ (2.20)	$ 0.08
Increase (Decrease) in ceiling test write-downs			$ 28,100				$ 53,500		$ 20,100		$ 35,400		$ 0	$ 137,100	$ 18,907

[1] Loss from operations and net loss available to common stockholders reported during the three months ended March 31, June 30, September 30 and December 31, 2012 included ceiling test write-downs of $20.1 million, $53.5 million, $35.4 million and $28.1 million, respectively.