The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount of accumulated impairment loss for 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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Goodwill and Amortizable Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Net carrying amount	$ 316,405		$ 316,405		$ 333,075
Amortization expense	20,800	$ 19,200	61,800	$ 38,100
In Process Capitalized Technology and Content Development
Finite-Lived Intangible Assets [Line Items]
Net carrying amount	37,300		37,300		30,700
Alternative Credential Segment
Finite-Lived Intangible Assets [Line Items]
Goodwill, accumulated impairment loss	$ 70,400		$ 70,400		$ 70,400