Stockholders' Equity - Additional Information (Details) (USD $)	1 Months Ended	3 Months Ended			1 Months Ended
	Oct. 31, 2012	Mar. 31, 2014	Mar. 31, 2013 Subsidiary	Mar. 31, 2014 Series B Preferred Stock [Member]	Jul. 31, 2013 Series A Preferred Stock [Member]	Mar. 31, 2014 Preferred Stock [Member]	Dec. 31, 2013 Preferred Stock [Member]	Mar. 31, 2014 Common Stock [Member]
Class of Stock [Line Items]
Preferred dividends description		Dividends on our 4.0% Series B Convertible Preferred Stock accrue daily and are payable in cash as approved by the Board of Directors. Our 4.0% Series A Convertible Preferred Stock ceased accruing dividends as a result of redemption in August 2013.
Series A and Series B preferred stock dividend rate percentage				4.00%	4.00%
Dividends accrued						$ 2,000,000	$ 4,000,000	$ 7,000,000
Shares of preferred stock converted				1,702,390
Common stock issued during period on conversion of convertible securities				14,481,721
Fair value of conversions				298,000,000
Dividends declared per common share		$ 0.05	$ 0.05
Stock Repurchase Program, Authorized Amount	1,000,000,000
Stock Repurchase Program, Period in Force	2 years
Share repurchases payment		64,000,000
Shares repurchased during period		3,109,500
Stock Repurchase Program, Remaining Authorized Repurchase Amount		107,000,000
Number of Subsidiaries in which Noncontrolling Interests were Purchased			3
Payments to Noncontrolling Interests			$ 7,000,000