Commitments and Contingent Liabilities (Narrative) (Details) $ / shares in Units, shares in Millions					1 Months Ended		3 Months Ended		12 Months Ended
	Apr. 08, 2024 exchangeOffer	Mar. 28, 2024 USD ($) $ / shares	Mar. 05, 2024 EUR (€)	Sep. 13, 2023	Jun. 30, 2016 USD ($) shares	Jun. 30, 2015 USD ($) shares	Mar. 31, 2024 USD ($) shares	Dec. 31, 2023 USD ($) shares	Dec. 31, 2015 trust
Loss Contingencies [Line Items]
Minimum securities lending related collateral percentage							100.00%
Commitments and letters of credit							$ 274,955,100,000	$ 285,387,400,000
Resell agreements, period end amounts excluding effects of agreements reported net by counterparty							16,400,000,000	27,700,000,000
Repurchase agreement counterparty, amount at risk							0	$ 0
FDIC, special assessment							12,500,000
Loss contingency accrual							0
Escrow deposit							$ 2,800,000,000
Common stock, convertible, conversion price							1.5875
Visa Class A Common Stock | Visa
Loss Contingencies [Line Items]
Share price (in usd) | $ / shares		$ 279.08
Visa Class A Common Stock | Subsequent Event
Loss Contingencies [Line Items]
Potential exchange offer program, number of exchange offers | exchangeOffer	3
Potential exchange offer program, length of time between exchanges	12 months
Potential exchange offer program, claim reduction percentage	50.00%
Visa Class A Common Stock | Period One
Loss Contingencies [Line Items]
Potential exchange offer program, exchange ratio				0.3333
Visa Class A Common Stock | Period One | Subsequent Event
Loss Contingencies [Line Items]
Potential exchange offer program, conversion period	45 days
Visa Class A Common Stock | Period Two
Loss Contingencies [Line Items]
Potential exchange offer program, exchange ratio				0.6666
Visa Class A Common Stock | Period Two | Subsequent Event
Loss Contingencies [Line Items]
Potential exchange offer program, conversion period	90 days
Visa Class A Common Stock | Period Three | Subsequent Event
Loss Contingencies [Line Items]
Potential exchange offer program, conversion period	90 days
Visa Class B
Loss Contingencies [Line Items]
Visa redemption gain					$ 123,100,000	$ 99,900,000
Shares issued (in shares) | shares					1.1	1.0
Common stock shares held (in shares) | shares							4.1	4.1
Remaining Visa shares held by Northern Trust, original cost basis							$ 0	$ 0
Conversion of stock, amount converted		$ 1,800,000,000
Northern Trust Fiduciary Services (Guernsey) Limited | Subsidiaries
Loss Contingencies [Line Items]
Number of administrated trusts serving as trustee on | trust									2
Lower Limit
Loss Contingencies [Line Items]
Possible loss in future periods in excess of accrual							0
Upper Limit
Loss Contingencies [Line Items]
Possible loss in future periods in excess of accrual							25,000,000
Indemnification Agreement
Loss Contingencies [Line Items]
Credit loss liability							0	0
FDIC Special Assessment
Loss Contingencies [Line Items]
FDIC, special assessment								$ 84,600,000
Possible loss in future periods in excess of accrual							$ 12,500,000
Northern Trust Fiduciary Services (Guernsey) Limited
Loss Contingencies [Line Items]
Litigation settlement, amount awarded to other party | €			€ 187,500