Earnings (Loss) Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net income (loss)	$ 7,841	$ 5,513	$ 5,043	$ 7,804	$ (9,777)	$ (5,725)	$ (7,844)	$ (10,402)	$ 26,201	$ (33,748)	$ (134,336)
Denominator:
Weighted-average common shares outstanding, Basic (in shares)	115,024	114,523	114,116	113,590	113,217	112,640	112,183	111,599	114,318	112,415	110,769
Effect of potential dilutive common shares									3,306	0	0
Denominator:
Weighted-average commone chares outstanding, Diluted (in shares)	117,620	118,206	117,398	116,629	113,217	112,640	112,183	111,599	117,624	112,415	110,769
Earnings Per Share, Basic									$ 0.23	$ (0.30)	$ (1.21)
Earnings Per Share, Diluted									$ 0.22	$ (0.30)	$ (1.21)