Capital Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2011
Class of Stock [Line Items]
Preferred dividends description	Series A and Series B preferred stock - Dividends on our 4.0% Series A Convertible Preferred Stock and 4.0% Series B Convertible Preferred Stock (preferred stock) are accrued monthly and are payable in cash as approved by the Board of Directors
Series A and Series B preferred stock dividend rate percentage	4.00%
Preferred dividends accrued	$ 8
Series B Preferred Stock elected to convert	90,099
Common stock shares issued for conversion	760,945
Total fair value of the conversions	$ 14