Earnings (loss) Per Share - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013
Computation Of Earnings Per Share Line Items
Common stock issued in exchange for convertible notes	6	28
Aggregate principal amount of senior convertible notes exchanged		$ 240
6% Convertible Senior Notes
Computation Of Earnings Per Share Line Items
Aggregate principal amount of senior convertible notes exchanged	$ 51	$ 240
Debt instrument effective interest rate	6.00%	6.00%
Due date of debt instrument	2029	2029