Fair Values of Assets and Liabilities Fair Value of Assets & Liabilities (Non-Recurring) (Details 5) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 158,687	$ 151,828
Nonconsolidated VIEs [Member] | Affordable housing partnerships and other real estate partnerships[Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	202	270
Nonconsolidated VIEs [Member] | Affordable housing partnerships and other real estate partnerships[Member] | Non-recurring basis [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 99	$ 158