Stockholders Equity - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 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	$ 8
Quarterly dividend declared	$ 0.05
Dividend declared and paid	$ 7