Notes Payable, Collateralized and Short-Term Borrowings - Summary of Company's Convertible Notes (Detail) (USD $) In Thousands, except Share data, unless otherwise specified			9 Months Ended	12 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 4.50% Convertible Notes [Member]	Dec. 31, 2012 4.50% Convertible Notes [Member]	Jul. 29, 2011 4.50% Convertible Notes [Member]	Sep. 30, 2013 8.75% Convertible Notes [Member]	Dec. 31, 2012 8.75% Convertible Notes [Member]	Sep. 30, 2012 8.75% Convertible Notes [Member]	Apr. 01, 2010 8.75% Convertible Notes [Member]
Schedule Of Short Term And Long Term Debt [Line Items]
Principal amount of debt component			$ 160,000	$ 160,000	$ 160,000	$ 150,000	$ 150,000		$ 150,000
Unamortized discount			(13,272)	(16,646)
Carrying amount of debt component	422,990	451,444	146,728	143,354		150,000	150,000
Equity component			18,972	18,972
Effective interest rate			7.61%	7.61%		8.75%	8.75%	8.75%
Maturity date (period through which discount is being amortized)			Jul. 15, 2016	Jul. 15, 2016		Apr. 15, 2015	Apr. 15, 2015
Conversion price			$ 9.84	$ 9.84		$ 6.34	$ 6.41
Number of shares to be delivered upon conversion			16,260,160	16,260,160		23,652,444	23,384,070
Amount by which the notes' if-converted value exceeds their principal amount