Bank Loans and Related Allowance for Credit Losses (Convert to Amortizing Loans) (Details) - HELOCs [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
HELOCs converted to amortizing loans	$ 11	$ 25
Converted to an amortizing loan by period end	475
Within 1 year	43
1 year – 3 years	83
3 years – 5 years	138
5 years	328
Total	$ 1,067