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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Prepayment speed	6.90%	6.30%	7.10%	6.20%
Weighted average life (in years)	3176 days	5804 days	3212 days	5840 days
Discount rate (annual rate)	10.80%	10.70%	10.90%	10.70%