Key economic assumptions used in measuring the servicing rights retained at the date of the residential mortgage loan securitizations and whole loan sales by the banking subsidiaries (Detail)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assumption For Fair Value On Securitization Date Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Discount Rate	11.50%	11.40%
Residential Mortgage
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Assumption For Fair Value On Securitization Date Of Interests Continued To Be Held By Transferor Servicing Assets Or Liabilities Prepayment Speed	5.60%	4.90%
Weighted average life (in years)	17.8	20.6