Goodwill and Acquired Intangible Assets (Tables)

9 Months Ended

Sep. 30, 2016

The components of acquired intangible assets as of September 30, 2016 and December 31, 2015 were as follows:

	September 30, 2016							December 31, 2015
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Value		Gross Carrying Amount		Accumulated Amortization			Net Carrying Value
	(in thousands)
Developed technology	$	10,640	$	(9,097	)	$	1,543	$	9,819	$	(6,288	)	$	3,531
Customer and vendor relationships, databases		282,751		(56,242	)		226,509		236,238		(44,192	)		192,046
Trademarks		969		(474	)		495		529		(215	)		314
Other		250		(42	)		208		—		—			—
Total amortizable intangible assets		294,610		(65,855	)		228,755		246,586		(50,695	)		195,891
Indefinite-lived trademarks		89,676		—			89,676		89,676		—			89,676
Total acquired intangible assets	$	384,286	$	(65,855	)	$	318,431	$	336,262	$	(50,695	)	$	285,567

Changes in the carrying amount of goodwill during the nine months ended September 30, 2016 were as follows:

	Goodwill		Accumulated Impairment Losses		Net Book Value
	(in thousands)
Balance as of December 31, 2015		396,220		—		396,220
Acquisitions		40,789		—		40,789
Balance as of September 30, 2016	$	437,009	$	—	$	437,009

The components of the acquired intangibles assets added during the nine months ended September 30, 2016 were as follows:

	Nine Months Ended September 30, 2016		Weighted-Average Amortization Period
	(in thousands)		(years)
Customer and vendor relationships	$	46,513		20.0
Developed technology		1,731		1.0
Trademarks		440		2.0
Total	$	48,684

Estimated future amortization expense of acquired intangible assets as of September 30, 2016 was as follows: