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) (Residential Mortgage)	3 Months Ended	12 Months Ended
	Jun. 30, 2011 Year	Dec. 31, 2010 Year
Residential Mortgage
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Prepayment speed	4.90%	5.90%
Weighted average life (in years)	20.3	17.1
Discount rate (annual rate)	11.50%	11.40%