Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Acquisitions and Divestitures - Summary of the Allocation of the Purchase Price to the Fair Value of the Assets and Liabilities Assumed, TOPO (Details) - USD ($) $ in Thousands	Oct. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets:
Goodwill		$ 2,945,547	$ 2,937,726	$ 2,923,136
TOPO
Assets:
Cash	$ 1,281
Fees receivable	1,402
Prepaid expenses and other assets	166
Goodwill	19,293
Finite-lived intangible assets	5,250
Total assets acquired	27,392
Total liabilities assumed (primarily deferred revenues)	2,417
Net assets acquired	$ 24,975
TOPO \| Customer Relationships
Business Acquisition [Line Items]
Acquired finite-lived intangible assets useful life	6 years
TOPO \| Content
Business Acquisition [Line Items]
Acquired finite-lived intangible assets useful life	1 year 6 months