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	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]
Prepayment speed	4.40%	5.40%
Weighted average life (in years)	10 years 11 months	10 years
Discount rate (annual rate)	11.00%	11.10%

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

3 Months Ended

Mar. 31, 2017

Mar. 31, 2016

Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items]

Prepayment speed

4.40%

5.40%

Weighted average life (in years)

10 years 11 months

10 years

Discount rate (annual rate)

11.00%

11.10%