Key Economic Assumptions Used to Estimate the Fair Value of MSRs Derived from Sales and Securitizations of Mortgage Loans Performed by the Banking Subsidiaries (Detail) (Residential Mortgage, Originated Mortgage Servicing Rights MSR, USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2011 Year	Dec. 31, 2010 Year
Residential Mortgage | Originated Mortgage Servicing Rights MSR
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of retained interests	$ 102,427	$ 101,675
Weighted average life (in years)	11,700	12,500
Weighted average prepayment speed (annual rate)	8.60%	8.00%
Impact on fair value of 10% adverse change	(3,671)	(3,413)
Impact on fair value of 20% adverse change	(7,113)	(6,651)
Weighted average discount rate (annual rate)	12.60%	12.80%
Impact on fair value of 10% adverse change	(4,541)	(4,479)
Impact on fair value of 20% adverse change	$ (8,690)	$ (8,605)