Calculation of Net Income (Loss) and Number of Shares Used to Compute Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income (loss)	$ (220,872)	$ (123,603)	$ 85,248
Net income (loss) per share - basic	$ (1.34)	$ (0.93)	$ 0.75
Weighted average shares outstanding - basic	164,964	132,375	113,020
Dilutive stock options			572
Restricted stock and restricted stock units			1,142
Weighted average shares outstanding - diluted	164,964	132,375	114,734
Net income (loss) per share - diluted	$ (1.34)	$ (0.93)	$ 0.74