Securitizations and Variable Interest Entities (Activity in Affordable Housing Program Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Securitizations And Variable Interest Entities [Abstract]
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ 109	$ 86	$ 61
Amortization Method Qualified Affordable Housing Project Investments, Amortization	90	72	51
Affordable Housing Project Investment, Write-down, Amount	0	0	$ 0
Investments in qualified affordable housing projects	1,095	830
Qualified Affordable Housing Project Investments, Commitment	$ 525	$ 372