Fair Values of Assets and Liabilities Fair Value of Assets & Liabilities (Non-Recurring) (Details 5) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets and liabilities measured at fair value
Total assets	$ 171,703	$ 165,883
Non-recurring basis | Level 2 | Commercial mortgage loans
Assets and liabilities measured at fair value
Loans held for sale	101
Non-recurring basis | Level 2 | Syndicated loans
Assets and liabilities measured at fair value
Loans held for sale	265
VIE, not primary beneficiary | Affordable housing partnerships
Assets and liabilities measured at fair value
Total assets	166	200
VIE, not primary beneficiary | Affordable housing partnerships | Non-recurring basis | Level 3
Assets and liabilities measured at fair value
Total assets	$ 100	$ 101