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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Intangible Assets and Goodwill - Intangible Assets, Net (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Intangible assets
Amortization of Acquired Intangible Assets		$ 224	$ 896
Indefinite-lived intangible assets		48,700		$ 48,700
Non-cash impairment charge, indefinite-lived		$ 18,677	$ 13,000
IPR&D
Intangible assets
Non-cash impairment charge, indefinite-lived	$ 11,800
License Rights
Intangible assets
Non-cash impairment charge, finite lived	$ 6,900