Clearing Operations (Schedule of Clearing Member Default Fund Contributions And Margin Deposits) (Details) - USD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Clearing Operations [Line Items]
Default fund contributions	$ 428
Margin deposits	7,457
Total	7,885
Cash Contributions
Clearing Operations [Line Items]
Default fund contributions	329
Margin deposits	1,994
Total	2,323	$ 5,842
Non-Cash Contributions
Clearing Operations [Line Items]
Default fund contributions	99
Margin deposits	5,463
Total	$ 5,562