Condensed Consolidated Statements of Income (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Transaction fees	$ 256.4	$ 126.2
Access fees	17.8	13.2
Exchange services and other fees	15.4	11.4
Market data fees	22.5	8.0
Regulatory fees	38.3	9.1
Other revenue	5.8	2.6
Total Revenues	356.2	170.5
Cost of Revenues:
Liquidity payments	105.3	6.6
Routing and clearing	6.3	1.7
Section 31 fees	30.0	0.0
Royalty fees	21.2	19.1
Total Cost of Revenues	162.8	27.4
Revenues less Cost of Revenues	193.4	143.1
Operating Expenses:
Compensation and benefits	47.8	27.1
Depreciation and amortization	25.1	11.9
Technology support services	7.5	5.7
Professional fees and outside services	14.4	13.6
Travel and promotional expenses	3.3	2.5
Facilities costs	2.1	1.5
Acquisition-related costs	65.2	0.0
Change in contingent consideration	0.2	0.0
Other expenses	1.7	1.3
Total Operating Expenses	167.3	63.6
Operating Income	26.1	79.5
Non-operating (Expenses) Income:
Interest (expense) income, net	(7.9)	0.7
Other income	0.1	0.3
Income Before Income Tax Provision	18.3	80.5
Income tax provision	3.1	31.3
Net income	15.2	49.2
Net loss attributable to noncontrolling interests	0.3	0.2
Net Income Excluding Noncontrolling Interests	15.5	49.4
Change in redemption value of noncontrolling interests	(0.3)	0.0
Net income allocated to participating securities	(0.1)	(0.2)
Net Income Allocated to Common Stockholders	$ 15.1	$ 49.2
Net Income Per Share Allocated to Common Stockholders:
Basic earnings per share (in USD per share)	$ 0.16	$ 0.60
Diluted earnings per share (in USD per share)	$ 0.16	$ 0.60
Basic weighted average shares outstanding (in shares)	91.9	81.8
Diluted weighted average shares outstanding (in shares)	92.0	81.8