Business Segments (Schedule of Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting [Line Items]
Total revenues	$ 2,532	$ 2,101	$ 4,670	$ 4,196
Transaction-based expenses	(1,032)	(795)	(1,762)	(1,653)
Revenues less transaction-based expenses	1,500	1,306	2,908	2,543
Directly consumed expenses	540	484	1,036	939
Other expenses	248	254	503	489
Operating income	712	568	1,369	1,115
Depreciation and amortization	165	158	331	313
Purchases of property and equipment	77	59	137	108
Operating segments | Capital Access Platforms
Segment Reporting [Line Items]
Total revenues	621	520	1,186	1,028
Directly consumed expenses	185	172	356	333
Other expenses	42	41	87	81
Operating income	394	307	743	614
Depreciation and amortization	12	11	39	21
Purchases of property and equipment	15	15	31	28
Operating segments | Financial Technology
Segment Reporting [Line Items]
Total revenues	539	464	1,057	896
Directly consumed expenses	255	220	488	426
Other expenses	34	27	73	56
Operating income	250	217	496	414
Depreciation and amortization	20	13	23	25
Purchases of property and equipment	35	29	68	51
Operating segments | Market Services
Segment Reporting [Line Items]
Total revenues	1,372	1,101	2,419	2,240
Transaction-based expenses	(1,032)	(795)	(1,762)	(1,653)
Revenues less transaction-based expenses	340	306	657	587
Directly consumed expenses	100	92	192	180
Other expenses	22	20	46	40
Operating income	218	194	419	367
Depreciation and amortization	11	11	25	22
Purchases of property and equipment	27	15	38	29
Corporate
Segment Reporting [Line Items]
Total revenues	0	16	8	32
Directly consumed expenses	150	166	297	312
Other expenses	150	166	297	312
Operating income	(150)	(150)	(289)	(280)
Depreciation and amortization	$ 122	$ 123	$ 244	$ 245