Bank Loans and Related Allowance for Loan Losses (Convert to Amortizing Loans) (Details) - Home equity loans and lines of credit [Member] $ in Millions	Sep. 30, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Converted to an amortizing loan by period end	$ 447
Within 1 year	475
1 year – 3 years	346
3 years – 5 years	148
5 years	626
Total	$ 2,042