Commitments and Contingencies - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) Lease	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Loss Contingencies [Line Items]
Number of operating leases	2
Rent expense \| $	$ 3,889	$ 2,207	$ 2,082
Contributions percentage of employees' salary	2.00%	2.00%	2.00%
Percentage of employees' contribution	50.00%	50.00%	50.00%
Capped percentage of employees' salary	4.00%	4.00%	4.00%
Company contributions \| $	$ 289	$ 259	$ 231
Midtown Manhattan [Member]
Loss Contingencies [Line Items]
Number of operating leases	1
Lease expiration date	Oct. 31, 2025
White Plains [Member]
Loss Contingencies [Line Items]
Number of operating leases	1
Lease expiration date	Jun. 30, 2023

Defined benefit plan percentage of employee contribution.

No definition available.

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- Definition

Defined benefit plan percentage of employee salary.

+ References

No definition available.

+ Details

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- Definition

Number of Operating Leases.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of contributions made by the employer to defined benefit plans.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(ii)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

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- Definition

Date which lease or group of leases is set to expire, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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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.

+ References

No definition available.

+ Details

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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717

+ Details

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Balance Type:	debit
Period Type:	duration

- Details

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- Details

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