Note Transfers of financial assets and servicing rights (Key economic assumptions used in measuring the SR retained at the date of the residential mortgage loan securitizations and whole loan sales by the banking subs) (Detail) - Residential Mortgage	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Prepayment speed	5.20%	8.60%
Weighted average life (in years)	10 years 2 months	7 years 1 month
Discount rate (annual rate)	11.00%	11.10%