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	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net loss	$ (68,985)	$ (51,312)	$ (133,655)	$ (107,206)
Net loss per share - basic and diluted	$ (0.37)	$ (0.31)	$ (0.74)	$ (0.66)
Weighted average shares - basic and diluted	184,726	165,848	181,651	163,409