Fair Value of Each Option Award Estimated on Date of Grant Using Black-Scholes-Merton Option-Pricing Formula (Detail)	12 Months Ended
	Dec. 31, 2011 Year	Dec. 31, 2010 Year	Dec. 31, 2009 Year
Schedule of Benefit Obligations Weighted Average Assumptions [Line Items]
Expected volatility	61.70%	59.50%	51.70%
Expected volatility	71.90%	67.60%	64.90%
Dividend yield	1.25%	0.90%	1.25%
Dividend yield	2.25%	1.20%	1.49%
Expected life	3.5	3.5	3.5
Expected life	4.6	4.6	4.6
Risk-free interest rate	0.39%	0.68%	1.23%
Risk-free interest rate	2.18%	2.30%	1.84%