Additional disclosures on cash flow information and non-cash activities (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Cash Flow Noncash Investing And Financing Activities Disclosure Abstract
Transfers Of Loans To Other Real Estate Owned	$ 218,798		$ 139,807
Transfers Of Loans To Other Property	18,970		20,690
Total loans transferred to foreclosed assets	237,768		160,497
Transfer Of Portfolio Loans And Leases To Held For Sale 1	55,826		53,618
Transfer Of Loans Held For Sale To Portfolio Loans 1	10,325		27,234
Noncash Transfer To Securities From Loans Resulting From Securitization	834,352	[1]	829,927	[1]
Write Downs Related To Loans Transferred To Loans Held For Sale	0		0
Trades receivables from brokers and counterparties	287,322		855,567		69,535
Trades Payables To Brokers And Counterparties	71,698		0
Recognition of mortgage servicing rights on securitizations or asset transfers	12,842		15,651
Payables Due To Counterparties Related To Early Extinguishment Of Debt	0		0
Loans sold to a joint venture in exchange for an acquisition loan and an equity interest in the join venture	0		102,353
Additional Cash Flow Elements Financing Activities Abstract
Conversion Of Stock Amount Converted 1	0		0
Conversion Of Stock Amount Issued	$ 0		$ 0

[1] Includes loans securitized into trading securities and subsequently sold before quarter end.