Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic EPS
Net loss available to common stockholders	$ 37,550	$ (15,821)	$ 22,973	$ 3,975	$ 11,364	$ 31,060	$ 38,611	$ 12,464	$ 48,677	$ 93,499	$ (91,308)
Net Income available to common stockholders, Shares									89,437,000	89,383,000	87,185,000
Net Income available to common stockholders, Per-Share	$ 0.42	$ (0.18)	$ 0.26	$ 0.04	$ 0.13	$ 0.35	$ 0.43	$ 0.14	$ 0.54	$ 1.05	$ (1.05)
Effect of Dilutive Securities
Equity awards, Income									0	0
Equity awards, Shares									166,000	342,000
Diluted EPS
Net loss available to common stockholders	$ 37,550	$ (15,821)	$ 22,973	$ 3,975	$ 11,364	$ 31,060	$ 38,611	$ 12,464	$ 48,677	$ 93,499	$ (91,308)
Net income available to common stockholders, shares									89,603,000	89,725,000	87,185,000
Net Income available to common stockholders, Per-Share	$ 0.42	$ (0.18)	$ 0.26	$ 0.04	$ 0.13	$ 0.35	$ 0.43	$ 0.14	$ 0.54	$ 1.04	$ (1.05)
Stock Options [Member]
Earnings Per Share (Textual) [Abstract]
Number of shares of common stock equivalents related to convertible debt									479,767	4,258	496,291
Convertible Debt [Member]
Earnings Per Share (Textual) [Abstract]
Number of shares of common stock equivalents related to convertible debt										1,059,228	1,296,231
Convertible Senior Notes Due March 2028 [Member]
Earnings Per Share (Textual) [Abstract]
Debt Instrument, Interest Rate, Stated Percentage	3.25%				3.25%				3.25%	3.25%