Fair Value of Each Award Estimated on Date of Grant Using Black-Scholes-Merton Option-Pricing Formula (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Expected volatility, min	56.20%	56.90%	67.30%
Expected volatility, max	63.70%	70.10%	72.90%
Dividend yield, min	0.00%	0.00%	2.25%
Dividend yield, max	0.00%	0.00%	4.98%
Risk-free interest rate, min	0.82%	0.34%	0.36%
Risk-free interest rate, max	1.63%	0.58%	0.51%
Stock Options | Minimum
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Expected life	3 years 6 months	3 years 6 months	3 years 6 months
Stock Options | Maximum
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Expected life	4 years 7 months	4 years 7 months	4 years 7 months
Performance Based Restricted Stock Units (PBRSUs)
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Expected volatility, min	52.60%	51.30%	29.30%
Expected volatility, max	72.30%	66.70%	78.00%
Dividend yield, min	0.00%	0.00%	0.00%
Dividend yield, max	0.00%	0.00%	5.30%
Risk-free interest rate, min	0.02%	0.01%	0.02%
Risk-free interest rate, max	1.07%	0.78%	0.43%