Bank Loans and Related Allowance for Loan Losses (Convert to Amortizing Loans) (Details) - HELOCs [Member] $ in Millions	Mar. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Converted to an amortizing loan by period end	$ 640
Within 1 year	66
1 year – 3 years	98
3 years – 5 years	173
5 years	417
Total	$ 1,394