Other assets - Qualified Affordable Housing Project Investments (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Other Assets [Abstract]
Qualified affordable housing project investments	$ 1,258			$ 1,258		$ 1,153
Qualified affordable housing project investments, commitment	623			623		$ 543
Qualified affordable housing project commitment - remainder of 2022	150			150
Qualified affordable housing project commitment - 2023	205			205
Qualified affordable housing project commitment - 2024	125			125
Qualified affordable housing project commitment - 2025	90			90
Qualified affordable housing project commitment - 2026	21			21
Qualified affordable housing project commitment - 2027 and thereafter	32			32
Tax credits and other tax benefits	38	$ 38	$ 38	76	$ 76
Amortization expense included in the provision for income taxes	$ 33	$ 32	$ 32	$ 65	$ 64