Goodwill and Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2017

Goodwill and Intangible Assets

Schedule of goodwill by segment

	Market		Execution
(in thousands)	Making		Services		Corporate		Total
Balance as of December 31, 2016	$	657,985	$	57,394	$	—	$	715,379
Additions		108,276		35,943		—		144,219
Balance as of September 30, 2017	$	766,261	$	93,337	$	—	$	859,598

Schedule of acquired intangible assets

	As of September 30, 2017
	Gross
	Carrying		Accumulated		Net Carrying		Useful Lives
(in thousands)	Amount		Amortization		Amount		(Years)
Purchased technology	$	110,000	$	110,000	$	—	1.4	to	2.5
ETF issuer relationships		950		533		417		9
ETF buyer relationships		950		533		417		9
Leases		1,800		247		1,553		3
FCC licenses		200		12		188		7
Technology		67,800		5,001		62,799	1	to	6
Customer relationships		77,100		1,027		76,073	13	to	17
Trade names		5,000		98		4,902		10
Exchange memberships		6,400		—		6,400		Indefinite
	$	270,200	$	117,451	$	152,749

	As of December 31, 2016
	Gross
	Carrying		Accumulated		Net Carrying		Useful Lives
(in thousands)	Amount		Amortization		Amount		(Years)
Purchased technology	$	110,000	$	110,000	$	—	1.4	to	2.5
ETF issuer relationships		950		454		496		9
ETF buyer relationships		950		454		496		9
	$	111,900	$	110,908	$	992