Fair Value of Purchased MSRs, Their Related Valuation Assumptions and Sensitivity to Immediate Changes in Those Assumptions (Detail) (Residential Mortgage, Purchased 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 | Purchased 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	$ 60,192	$ 65,232
Weighted average life (in years)	11,700	12,700
Weighted average prepayment speed (annual rate)	8.60%	7.90%
Impact on fair value of 10% adverse change	(2,502)	(1,963)
Impact on fair value of 20% adverse change	(4,417)	(3,956)
Weighted average discount rate (annual rate)	11.50%	11.50%
Impact on fair value of 10% adverse change	(2,789)	(2,353)
Impact on fair value of 20% adverse change	$ (4,935)	$ (4,671)