Calculation of Net Income (Loss) and Number of Shares Used to Compute Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income (loss)	$ (53,213)	$ 13,910	$ (160,419)	$ (71,801)
Weighted-average shares outstanding - basic	166,296	132,587	164,378	131,215
Dilutive stock options		3,187
Restricted stock and restricted stock units		1,706
Weighted-average shares outstanding - diluted	166,296	137,480	164,378	131,215