Clearing Operations (Schedule of Derivative Contracts) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) TWh contract	Mar. 31, 2021 TWh contract
Clearing Operations [Line Items]
Market value of derivative contracts | $	$ 2,173
Total number of cleared contracts (in contracts) | contract	24,948,668	21,942,207
Total volume in cleared power, in Terawatt hours (TWh) | TWh	135	250
Commodity and seafood options, futures and forwards
Clearing Operations [Line Items]
Market value of derivative contracts | $	$ 518
Total number of cleared contracts (in contracts) | contract	96,153	155,662
Fixed-income options and futures
Clearing Operations [Line Items]
Market value of derivative contracts | $	$ 1,345
Total number of cleared contracts (in contracts) | contract	6,594,330	6,404,204
Stock options and futures
Clearing Operations [Line Items]
Market value of derivative contracts | $	$ 228
Total number of cleared contracts (in contracts) | contract	5,113,644	6,306,308
Index options and futures
Clearing Operations [Line Items]
Market value of derivative contracts | $	$ 82
Total number of cleared contracts (in contracts) | contract	13,144,541	9,076,033