Earnings (loss) Per Common Share (Reconciliation of Earnings (loss) Per Common Share) (Details) (USD $) In Thousands, except Per 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
Net income (loss)	$ 3,560	$ 2,615	$ 9,685	$ 14,172	$ 6,818	$ 6,744	$ 3,650	$ (6,035)	$ 30,032	$ 11,177	$ (33,261)
Weighted-average shares, outstanding									61,780	57,390	53,797
Income (loss) per share	$ 0.06	$ 0.04	$ 0.16	$ 0.23	$ 0.11	$ 0.11	$ 0.07	$ (0.11)	$ 0.49	$ 0.19	$ (0.62)
Diluted
Net income (loss)	$ 3,560	$ 2,615	$ 9,685	$ 14,172	$ 6,818	$ 6,744	$ 3,650	$ (6,035)	$ 30,032	$ 11,177	$ (33,261)
Weighted average shares:
Weighted-average shares, outstanding									61,780	57,390	53,797
Diluted effect of stock options, restricted stock, and restricted stock unit awards									982	1,389	0
Weighted-average shares, Diluted									62,762	58,779	53,797
Income (loss) per share	$ 0.06	$ 0.04	$ 0.15	$ 0.23	$ 0.11	$ 0.11	$ 0.07	$ (0.11)	$ 0.48	$ 0.19	$ (0.62)