Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)
Significant Accounting Policies [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	10.00%
Number of Operating Segments \| segment	1
Accrued fees to authorized agents	$ 3,300,000	$ 2,700,000
Loss Contingency Accrual	$ 0
Computers and equipment
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Computer software
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Furniture and fixtures
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Minimum \| Leasehold improvements
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Maximum \| Leasehold improvements
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	14 years

[Line Items] for Significant Accounting Policies [Table]

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- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
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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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Amount of expenses incurred but not yet paid classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.15(a))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
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-URI http://asc.fasb.org/extlink&oid=118582676&loc=SL6759159-111685

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