Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Commission Revenue by Fee Type

The following table presents commission revenue by fee type for the three years ended December 31, 2018:

	Year Ended December 31,
	2018		2017		2016
	(In thousands)
Commission revenue by fee type
Variable transaction fees
Disclosed trading	$	228,004	$	234,143	$	230,319
Open Trading - matched principal trading		65,932		45,660		37,747
Total variable transaction fees		293,936		279,803		268,066
Distribution fees and unused minimum fees		96,898		75,479		64,241
Total commissions	$	390,834	$	355,282	$	332,307

Summary of Information Services Revenue by Timing of Recognition

The following table presents information services revenue by timing of recognition for the three years ended December 31, 2018:

	Year Ended December 31,
	2018		2017		2016
	(In thousands)
Information services revenue by timing of recognition
Services transferred over time	$	27,475	$	25,242	$	22,011
Services transferred at a point in time		752		564		1,258
Total information services revenues	$	28,227	$	25,806	$	23,269

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 years ended December 31, 2018:

	Year Ended December 31,
	2018		2017		2016
	(In thousands)
Post-trade services revenue by timing of recognition
Services transferred over time	$	15,013	$	9,657	$	10,812
Services transferred at a point in time		333		1,433		—
Total post-trade services revenues	$	15,346	$	11,090	$	10,812

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			December 31, 2018
	(In thousands)
Information services	$	1,763	$	7,109	$	(6,913	)	$	—		$	1,959
Post-trade services		897		11,566		(11,561	)		(51	)		851
Total deferred revenue	$	2,660	$	18,675	$	(18,474	)	$	(51	)	$	2,810