Earnings Per Share - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended				9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012 Maximum [Member]	Sep. 30, 2012 Convertible Notes [Member]	Sep. 30, 2012 Convertible Notes [Member]	Sep. 30, 2012 Stock Awards [Member]	Sep. 30, 2012 Stock Awards [Member]	Sep. 30, 2012 Stock Option [Member]	Sep. 30, 2013 Stock Option [Member]	Sep. 30, 2012 Stock Option [Member]	Sep. 30, 2013 Stock and Performance Awards [Member]	Sep. 30, 2012 Stock and Performance Awards [Member]	Sep. 30, 2013 Equity Unit Purchase Agreements [Member]	Sep. 30, 2012 Equity Unit Purchase Agreements [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Participating securities outstanding	0	0	1
Participating securities outstanding, nonforfeitable											16	12
Number of anti-dilutive securities	89	89		89	89	7	6	3		4			48	27
Shares that would have been included in diluted earnings per share calculation				89	89	12	11	18		20
Weighted average exercise price of options									$ 10.78	$ 15.42