Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Summary of Commission Revenue by Fee Type

The following table presents commission revenue by fee type for the three and six months ended June 30, 2018 and 2017:

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
	(In thousands)
Commission revenue by fee type
Variable transaction fees
Disclosed trading	$	56,463	$	59,367	$	122,716	$	125,270
Open Trading™ - matched principal trading		15,191		11,216		28,715		23,161
Total variable transaction fees		71,654		70,583		151,431		148,431
Distribution fees and unused minimum fees		24,459		16,432		47,454		32,606
Total commissions	$	96,113	$	87,015	$	198,885	$	181,037

Summary of Information Services Revenue by Timing of Recognition

The following table presents information services revenue by timing of recognition for the three and six months ended June 30, 2018 and 2017:

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
	(In thousands)
Information services revenue by timing of recognition
Services transferred over time	$	6,829	$	6,287	$	13,623	$	12,332
Services transferred at a point in time		101		210		373		350
Total information services revenues	$	6,930	$	6,497	$	13,996	$	12,682

Summary of Post-Trade Services Revenue by Timing of Recognition

The following table presents post-trade services revenue by timing of recognition for the three and six months ended June 30, 2018 and 2017:

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
	(In thousands)
Post-trade services revenue by timing of recognition
Services transferred over time	$	3,620	$	2,470	$	7,907	$	4,919
Services transferred at a point in time		—		19		289		26
Total post-trade services revenues	$	3,620	$	2,489	$	8,196	$	4,945

Summary of Revenue Recognized from Contract Liabilities and Remaining Balance

The revenue recognized from contract liabilities and the remaining balance is shown below:

	December 31, 2017		Payments received in advance of services to be performed		Revenue recognized for services performed during the period			Foreign Currency Translation			June 30, 2018
	(In thousands)
Information services	$	1,763	$	3,752	$	(3,312	)	$	—		$	2,203
Post-trade services		897		6,423		(5,908	)		(20	)		1,392
Total deferred revenue	$	2,660	$	10,175	$	(9,220	)	$	(20	)	$	3,595