Goodwill and Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of changes to the carrying amount of goodwill by reporting unit

The following table presents changes to the carrying amount of goodwill by segment during the three months ended March 31, 2019 (in thousands):

	Research			Conferences			Consulting		Total
Balance at December 31, 2018 (1)	$	2,638,418		$	187,654		$	97,064	$	2,923,136
Foreign currency translation impact	(16,386		)	(61		)	47		(16,400		)
Balance at March 31, 2019	$	2,622,032		$	187,593		$	97,111	$	2,906,736

(1) The Company does not have any accumulated goodwill impairment losses.

Schedule of amortizable intangible assets

The following tables present reconciliations of the carrying amounts of the Company's finite-lived intangible assets as of the dates indicated (in thousands):

March 31, 2019	Customer Relationships			Software			Content			Other			Total
Gross cost at December 31, 2018	$	1,131,656		$	110,701		$	98,842		$	51,662		$	1,392,861
Intangible assets fully amortized	—			—			(85,894		)	—			(85,894		)
Foreign currency translation impact	8,344			278			—			61			8,683
Gross cost	1,140,000			110,979			12,948			51,723			1,315,650
Accumulated amortization (1)	(210,203		)	(44,632		)	(7,877		)	(36,883		)	(299,595		)
Balance at March 31, 2019	$	929,797		$	66,347		$	5,071		$	14,840		$	1,016,055

December 31, 2018	Customer Relationships			Software			Content			Other			Total
Gross cost	$	1,131,656		$	110,701		$	98,842		$	51,662		$	1,392,861
Accumulated amortization (1)	(184,918		)	(38,901		)	(92,717		)	(33,760		)	(350,296		)
Balance at December 31, 2018	$	946,738		$	71,800		$	6,125		$	17,902		$	1,042,565

(1) Finite-lived intangible assets are amortized using the straight-line method over the following periods: Customer relationships—4 to 13 years; Software—3 to 7 years; Content—1.5 to 5 years; and Other—2 to 11 years.

Schedule of estimated future amortization expense by year

The estimated future amortization expense by year for finite-lived intangible assets is as follows (in thousands):

2019 (remaining nine months)	$	96,977
2020	124,391
2021	103,949
2022	94,410
2023	94,410
Thereafter	501,918
	$	1,016,055