Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data	Common Stock [Member]	Retained Earnings [Member]	Total
Balances at Dec. 31, 2011	$ 557,238	$ (334,786)	$ 222,452
Balances (in Shares) at Dec. 31, 2011	115,910,000
Long-term incentive compensation plans, net of forfeitures	2,841		2,841
Long-term incentive compensation plans, net of forfeitures (in Shares)	982,000
Common stock sold for cash, net of offering costs	96		96
Common stock sold for cash, net of offering costs (in Shares)	40,000
Net loss		(39,089)	(39,089)
Balances at Dec. 31, 2012	560,175	(373,875)	186,300
Balances (in Shares) at Dec. 31, 2012	116,932,000
Long-term incentive compensation plans, net of forfeitures	2,806		2,806
Long-term incentive compensation plans, net of forfeitures (in Shares)	568,000
Common stock sold for cash, net of offering costs	48		48
Common stock sold for cash, net of offering costs (in Shares)	26,000
Proceeds of convertible notes allocated to equity, net of debt issuance costs	6,032		6,032
Net loss		(57,711)	(57,711)
Balances at Dec. 31, 2013	569,061	(431,586)	137,475
Balances (in Shares) at Dec. 31, 2013	117,526,000		117,526,000
Exercise of stock options	129		129
Exercise of stock options (in Shares)	99,000		99,248
Long-term incentive compensation plans, net of forfeitures	3,163		3,163
Long-term incentive compensation plans, net of forfeitures (in Shares)	1,011,000
Common stock sold for cash, net of offering costs	37		37
Common stock sold for cash, net of offering costs (in Shares)	21,000
Proceeds of convertible notes allocated to equity, net of debt issuance costs	500		500
Net loss		(107,906)	(107,906)
Balances at Dec. 31, 2014	$ 572,890	$ (539,492)	$ 33,398
Balances (in Shares) at Dec. 31, 2014	118,657,000		118,657,000