Components of Asset-Backed Securities Issued by Consolidated Securitization Entities Sponsored, Along With Other Selected Information (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2013 Asset-backed Securities	Dec. 31, 2012 Asset-backed Securities	Sep. 30, 2013 Asset-backed Securities Certificates With Principal Value	Dec. 31, 2012 Asset-backed Securities Certificates With Principal Value	Sep. 30, 2013 Asset-backed Securities Interest Only Certificates	Dec. 31, 2012 Asset-backed Securities Interest Only Certificates	Sep. 30, 2013 Asset-backed Securities Sequoia Contract	Dec. 31, 2012 Asset-backed Securities Sequoia Contract	Sep. 30, 2013 Asset-backed Securities Sequoia Minimum	Dec. 31, 2012 Asset-backed Securities Sequoia Minimum	Sep. 30, 2013 Asset-backed Securities Sequoia Maximum	Dec. 31, 2012 Asset-backed Securities Sequoia Maximum	Sep. 30, 2013 Asset-backed Securities Sequoia Certificates With Principal Value	Dec. 31, 2012 Asset-backed Securities Sequoia Certificates With Principal Value	Sep. 30, 2013 Asset-backed Securities Sequoia Interest Only Certificates	Dec. 31, 2012 Asset-backed Securities Sequoia Interest Only Certificates	Sep. 30, 2013 Asset-backed Securities Resecuritization Contract	Dec. 31, 2012 Asset-backed Securities Resecuritization Contract	Sep. 30, 2013 Asset-backed Securities Resecuritization Certificates With Principal Value	Dec. 31, 2012 Asset-backed Securities Resecuritization Certificates With Principal Value	Sep. 30, 2013 Asset-backed Securities Commercial Securitization Contract	Dec. 31, 2012 Asset-backed Securities Commercial Securitization Contract	Sep. 30, 2013 Asset-backed Securities Commercial Securitization Certificates With Principal Value	Dec. 31, 2012 Asset-backed Securities Commercial Securitization Certificates With Principal Value
Debt Instrument [Line Items]
Principal value				$ 2,075,929	$ 2,544,311	$ 4,014	$ 7,769							$ 1,804,951	$ 2,207,851	$ 4,014	$ 7,769			$ 112,179	$ 164,746			$ 158,799	$ 171,714
Unamortized premium			921						921
Unamortized discount		(18,278)	(23,060)					(18,278)	(23,060)
Total ABS Issued		$ 2,061,665	$ 2,529,941					$ 1,790,687	$ 2,193,481									$ 112,179	$ 164,746			$ 158,799	$ 171,714
Weighted average interest rates, by series										0.33%	0.41%	4.22%	4.16%					2.21%	2.21%			5.62%	5.62%
Stated maturities	2018									2014	2014	2047	2047					2046	2046			2018	2018
Number of series								24	24									1	1			1	1