Stockholders' Equity - Additional Information (Details) (USD $)	0 Months Ended	3 Months Ended					9 Months Ended				0 Months Ended	3 Months Ended	9 Months Ended		1 Months Ended
	Jul. 02, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2013 Subsidiary	Sep. 30, 2014	Sep. 30, 2013	Jul. 30, 2014	Jun. 28, 2013	Sep. 30, 2014 Series B Preferred Stock [Member]	Sep. 30, 2014 Series B Preferred Stock [Member]	Sep. 29, 2014 Series B Preferred Stock [Member]	Sep. 30, 2014 Series B Preferred Stock [Member]	Jul. 31, 2013 Series A Preferred Stock [Member]	Sep. 30, 2014 Preferred Stock [Member]	Dec. 31, 2013 Preferred Stock [Member]
Class of Stock [Line Items]
Preferred dividends description							Our 4.0% Series B Convertible Preferred Stock ceased accruing dividends as a result of the conversion of all of the remaining outstanding shares on September 30, 2014. 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
Shares of preferred stock converted											1,506,972	1,772,693	2,296,802
Common stock issued during period on conversion of convertible securities											12,631,780		19,517,593
Fair value of conversions											250,000,000		409,000,000
Terms of conversion - closing price of common stock	$ 22.24
Terms of conversion - consecutive trading days	20 days
Conversion Notice Period	90 days
Dividends declared per common share		$ 0.05	$ 0.05	$ 0.05	$ 0.05		$ 0.15	$ 0.15
Treasury stock reissued during period		14,879,935
Charge to Additional Paid in Capital		127,000,000
Stock Repurchase Program, Authorized Amount									1,400,000,000	1,000,000,000
Repurchases of common stock							181,000,000	288,000,000
Shares repurchased during period							8,295,202
Stock Repurchase Program, Remaining Authorized Repurchase Amount		390,000,000					390,000,000
Number of subsidiaries in which Noncontrolling Interests were purchased						3
Payments to Noncontrolling Interests						$ 7,000,000		$ 7,000,000