Bank Loans and Related Allowance for Loan Losses (Convert to Amortizing Loans) (Details) - HELOCs [Member] $ in Millions	Sep. 30, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Converted to an amortizing loan by period end	$ 640
Within 1 year	186
1 year – 3 years	133
3 years – 5 years	163
5 years	480
Total	$ 1,602