Stockholders' Equity - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended				12 Months Ended				12 Months Ended	1 Months Ended			12 Months Ended			0 Months Ended	1 Months Ended	3 Months Ended
	Jun. 30, 2013	Oct. 31, 2012	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013 Subsidiary	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Beginning On or After January 31, 2013	Aug. 31, 2013 Series A Preferred Stock	Aug. 02, 2013 Series A Preferred Stock	Jan. 31, 2008 Series A Preferred Stock	Dec. 31, 2013 Series B Preferred Stock	Dec. 31, 2011 Series B Preferred Stock	Jan. 31, 2008 Series B Preferred Stock	Oct. 28, 2013 Accelerated Share Repurchase Program [Member]	Aug. 31, 2013 Accelerated Share Repurchase Program [Member]	Oct. 31, 2013 Accelerated Share Repurchase Program [Member]
Class of Stock [Line Items]
Preferred shares issued														2,500,000			5,400,000
Payment for preferred stock redemption							$ 474,000,000					$ 474,000,000
Payment of preferred stock redemption costs												3,000,000
Preferred stock carrying value													242,000,000
Preferred stock redemption premium				232,000,000			232,000,000					232,000,000
Common stock conversion price of preferred shares										$ 11.93
Common shares issuable for convertible outstanding preferred shares															31,900,000
Terms of conversion - closing price of common stock											$ 22.24
Terms of conversion - consecutive trading days											20 days
Preferred dividends description							Dividends on our 4.0% Series A Convertible Preferred Stock and 4.0% Series B Convertible Preferred Stock accrue daily 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							4,000,000	8,000,000
Shares of preferred stock converted															1,417,425	90,099
Common shares issued upon conversion															11,985,254	760,945
Total fair value of the conversions															249,000,000	14,000,000
Common stock, shares authorized			450,000,000				450,000,000	450,000,000
Common stock, par value			$ 0.01				$ 0.01	$ 0.01
Common stock, shares issued			164,080,630				164,080,630
Common stock, shares outstanding			145,338,342				145,338,342	148,264,067
Treasury stock, shares			18,742,288				18,742,288	1,797,988
Quarterly dividend declared			$ 0.05	$ 0.05	$ 0.05	$ 0.05	$ 0.2	$ 0.2	$ 0
Dividends declared and paid							30,000,000
Share repurchase program amount	1,000,000,000	250,000,000																	200,000,000
Stock Repurchase Program Period	2 years	2 years
Share Repurchases Payment							137,000,000
Shares repurchased							7,601,040
Accelerated Share Repurchases, Settlement (Payment) or Receipt																			200,000,000
Accelerated Share Repurchases, Initial Delivery Of Shares																			7,302,602
Accelerated Share Repurchases, Percentage Of Value Delivered In Initial Shares																			80.00%
Accelerated Share Repurchases, Initial Price Paid Per Share																			$ 21.91
Accelerated Share Repurchases Final Delivery Of Shares																		1,831,445
Accelerated Share Repurchases Total Delivery Of Shares																				9,134,047
Accelerated Share Repurchases, Final Price Paid Per Share																				$ 21.90
Available for future share repurchases							171,000,000
Number Of Subsidiaries In Which Noncontrolling Interests Were Purchased						3
Payments to Noncontrolling Interests						$ 7,000,000	$ 7,000,000