Stockholders' Equity - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended						12 Months Ended			1 Months Ended	7 Months Ended	0 Months Ended	9 Months Ended
	Jul. 02, 2014	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2013 Subsidiary	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 31, 2013	Jul. 31, 2013	Sep. 30, 2014	Sep. 29, 2014	Sep. 30, 2014	Jul. 30, 2014	Jun. 28, 2013	Aug. 02, 2013	Jan. 31, 2008
Class of Stock [Line Items]
Preferred dividends description								Our 4.0% Series A Convertible Preferred Stock ceased accruing daily dividends as a result of redemption in August 2013. Our 4.0% Series B Convertible Preferred Stock ceased accruing daily dividends as a result of the conversion of all of the remaining outstanding shares on September 30, 2014.
Preferred shares outstanding		0						0
Preferred dividends accrued									$ 4,000,000
Payment for preferred stock redemption									474,000,000
Preferred stock redemption premium						232,000,000			232,000,000
Terms of conversion - closing price of common stock	$ 22.24
Terms of conversion - consecutive trading days	20 days
Common stock conversion price of preferred shares	$ 11.93
Conversion Notice Period	90 days
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		167,659,047						167,659,047
Common stock, shares outstanding		166,070,057						166,070,057	145,338,342
Treasury stock, shares		1,588,990						1,588,990	18,742,288
Quarterly dividend declared		$ 0.05	$ 0.05	$ 0.05	$ 0.05			$ 0.20	$ 0.20	$ 0.20
Dividends declared and paid								32,000,000
Treasury stock reissued								14,879,935
Treasury stock reissued, charge to additional paid-in capital								127,000,000
Treasury shares retired								14,600,000
Treasury stock retired, charge to additional paid-in capital								0
Share repurchase program amount																1,400,000,000	1,000,000,000
Cash spent to repurchase common stock								260,000,000	337,000,000	15,000,000
Shares repurchased								12,215,451
Available for future share repurchases		311,000,000						311,000,000
Number of subsidiaries in which noncontrolling interests were purchased							3
Payments to Noncontrolling Interests							7,000,000		7,000,000
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred shares issued																			2,500,000.0
Series A and Series B preferred stock dividend rate percentage												4.00%
Preferred shares outstanding		0						0	0
Payment for preferred stock redemption											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
Preferred Stock [Member]
Class of Stock [Line Items]
Preferred dividends accrued									4,000,000
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred shares issued																			5,400,000.0
Series A and Series B preferred stock dividend rate percentage															4.00%
Preferred shares outstanding		0						0	3,803,774
Shares of preferred stock converted								1,772,693	1,417,425				1,506,972	2,296,802
Common shares issued upon conversion									11,985,254				12,631,780	19,517,593
Total fair value of the conversions									249,000,000				250,000,000	409,000,000
Additional Paid-in Capital [Member]
Class of Stock [Line Items]
Treasury stock retired, charge to additional paid-in capital								$ (294,000,000)