Stockholders Equity - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Jun. 30, 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	$ 0.10
Dividends declared and paid		$ 15