Condensed Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues:
Total revenues	$ 921.5	$ 602.6
Cost of revenues:
Total cost of revenues	563.2	322.1
Revenues less cost of revenues	358.3	280.5
Operating expenses:
Compensation and benefits	53.3	48.1
Depreciation and amortization	40.5	47.2
Technology support services	11.9	11.9
Professional fees and outside services	14.9	16.2
Travel and promotional expenses	2.1	2.6
Facilities costs	4.1	2.1
Acquisition-related costs	0.8	2.3
Other expenses	4.3	3.6
Total operating expenses	131.9	134.0
Operating income	226.4	146.5
Non-operating expenses:
Interest expense, net	(7.3)	(9.9)
Other expense, net	(1.6)	(8.8)
Income before income tax provision	217.5	127.8
Income tax provision	60.1	32.6
Net income	157.4	95.2
Net loss attributable to redeemable noncontrolling interest		0.2
Net income excluding redeemable noncontrolling interest	157.4	95.4
Change in redemption value of redeemable noncontrolling interest		(0.2)
Net income allocated to participating securities	(0.4)	(0.6)
Net income allocated to common stockholders	$ 157.0	$ 94.6
Basic earnings per share (in dollars per share)	$ 1.42	$ 0.85
Diluted earnings per share (in dollars per share)	$ 1.42	$ 0.85
Basic weighted average shares outstanding (in shares)	110.4	111.5
Diluted weighted average shares outstanding (in shares)	110.6	111.7
Transaction fees
Revenues:
Total revenues	$ 661.5	$ 430.4
Access and capacity fees
Revenues:
Total revenues	57.7	54.4
Market data fees
Revenues:
Total revenues	56.2	51.6
Regulatory fees
Revenues:
Total revenues	136.8	58.7
Other revenue
Revenues:
Total revenues	9.3	7.5
Liquidity payments
Cost of revenues:
Total cost of revenues	392.4	243.7
Routing and clearing
Cost of revenues:
Total cost of revenues	16.0	9.2
Section 31 fees
Cost of revenues:
Total cost of revenues	127.4	48.2
Royalty fees
Cost of revenues:
Total cost of revenues	$ 27.4	$ 21.0