Business Segment Information - Additional Information (Details) - segment	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Concentration Risk [Line Items]
Number of operating segments	1
AllianceBernstein Global High Yield Portfolio
Concentration Risk [Line Items]
Percentage of investment advisory and service fees	9.00%	10.00%	11.00%
Percentage of net revenues	9.00%	10.00%	12.00%
Customer Concentration Risk \| HSBC
Major Customers [Abstract]
Percentage of open-end mutual fund sales	14.00%	7.00%	9.00%
Customer Concentration Risk \| EQH, Equitable Life And Subsidiaries
Major Customers [Abstract]
Percentage of total revenues from general and separate accounts of affiliates	3.00%	3.00%	3.00%
Customer Concentration Risk \| AXA and subsidiaries
Major Customers [Abstract]
Percentage of total revenues from general and separate accounts of affiliates	2.00%	2.00%	2.00%
Percentage of total revenues from unaffiliated customer (more than)	1.00%	1.00%	1.00%

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- Definition

Percentage of total investment advisory fees recognized during the period.

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- Definition

Percentage of the total net revenue recognized during the period.

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- Definition

Percentage of open ended mutual fund sales that companies are responsible. (open ended mutual fund does not have restrictions on the amount of shares the fund will issue)

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- Definition

Percentage amount of total revenue deriving from affiliated companies general and separate accounts.

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- Definition

Maximum percentage amount of total revenue deriving from customers other than affiliated clients.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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