Intangible Assets, Net - Summary of Intangible Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Definite-lived intangible assets:
Investment contracts and other	$ 489,570	$ 487,747
Accumulated amortization	(215,162)	(192,451)
Definite-lived intangible assets, net	274,408	295,296
Indefinite-lived intangible assets	43,516	43,516
Total intangible assets, net	$ 317,924	$ 338,812	$ 346,353	$ 301,954

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

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

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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 assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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