Assumptions Used for Calculating Fair Values of Stock Option Awards (Detail) (USD $)	1 Months Ended	12 Months Ended
	Dec. 31, 1999	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Stock Options Granted
Weighted average grant date fair value, per share		$ 19.84	$ 17.35	$ 26.13
Weighted average assumptions used:
Expected volatility		66.40%	73.50%	70.10%
Expected lives	3 years	4 years 10 months 24 days	4 years 8 months 12 days	4 years 9 months 18 days
Risk-free interest rates		0.70%	0.80%	1.80%
Dividends yields		0.00%	0.00%	0.00%