Short-Term Borrowings - Schedule of Short-Term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Short-term Debt [Line Items]
Year-end balance	$ 2,549	$ 2,506
Trading Liabilities
Short-term Debt [Line Items]
Average balance	301	480	$ 540
Year-end balance	509	335	426
Maximum month-end outstanding	$ 509	$ 700	$ 685
Average rate for the year	4.16%	2.56%	1.11%
Average rate at year-end	4.48%	3.67%	1.62%
Federal Funds Purchased
Short-term Debt [Line Items]
Average balance	$ 349	$ 699	$ 949
Year-end balance	302	400	775
Maximum month-end outstanding	$ 622	$ 1,023	$ 1,037
Average rate for the year	5.12%	1.56%	0.12%
Average rate at year-end	5.40%	4.40%	0.10%
Securities Sold Under Agreements to Repurchase
Short-term Debt [Line Items]
Average balance	$ 1,426	$ 881	$ 1,235
Year-end balance	1,921	1,013	1,247
Maximum month-end outstanding	$ 1,957	$ 1,211	$ 1,615
Average rate for the year	3.66%	0.77%	0.30%
Average rate at year-end	3.98%	2.19%	0.11%
Other Short-term Borrowings
Short-term Debt [Line Items]
Average balance	$ 2,688	$ 229	$ 124
Year-end balance	326	1,093	102
Maximum month-end outstanding	$ 7,476	$ 1,093	$ 146
Average rate for the year	5.19%	2.26%	0.09%
Average rate at year-end	5.36%	4.30%	0.08%