Condensed Consolidated Statement of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Operating Revenues:
Transaction fees	$ 97,932	$ 106,094	$ 210,722	$ 205,239
Access fees	14,875	15,026	30,107	30,680
Exchange services and other fees	9,676	9,315	19,168	18,403
Market data fees	7,815	5,729	14,973	11,266
Regulatory fees	9,744	10,439	19,601	20,139
Other revenue	3,900	4,169	7,256	7,750
Total Operating Revenues	143,942	150,772	301,827	293,477
Operating Expenses:
Employee costs	30,306	31,237	63,680	62,074
Depreciation and amortization	9,895	8,622	18,499	16,904
Data processing	4,783	4,545	9,504	9,061
Outside services	7,855	9,633	15,233	20,668
Royalty fees	14,707	14,518	30,609	27,687
Trading volume incentives	1,120	908	2,246	1,921
Travel and promotional expenses	2,446	2,594	4,433	4,658
Facilities costs	1,590	1,247	2,903	2,500
Other expenses	1,524	2,110	2,966	3,216
Total Operating Expenses	74,226	75,414	150,073	148,689
Operating Income	69,716	75,358	151,754	144,788
Other Income/(Expense):
Investment income	12	18	26	22
Net loss from investment in affiliates	(333)	(491)	(842)	(1,217)
Total Other Expense	(321)	(473)	(816)	(1,195)
Income Before Income Taxes	69,395	74,885	150,938	143,593
Income tax provision	26,414	28,724	58,933	55,060
Net Income	42,981	46,161	92,005	88,533
Net Income allocated to participating securities	(383)	(684)	(879)	(1,268)
Net Income Allocated to Common Stockholders	$ 42,598	$ 45,477	$ 91,126	$ 87,265
Net income per share (Note 4):
Basic (in dollars per share)	$ 0.50	$ 0.52	$ 1.06	$ 1.00
Diluted (in dollars per share)	$ 0.50	$ 0.52	$ 1.06	$ 1.00
Weighted average shares used in computing income per share:
Weighted Average Number of Shares Outstanding, Basic	85,831	87,341	86,140	87,307
Weighted Average Number of Shares Outstanding, Diluted (in shares)	85,831	87,341	86,140	87,307