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- Definition

Limited partnership units exchange ratio.

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- Definition

Share-based compensation arrangement by share-based payment award, number of shares registered.

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No definition available.

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- Definition

Share based compensation arrangement by share based payment award units redeemed.

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No definition available.

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- Definition

The compensation expense recognized during the period pertaining to the deferred compensation arrangement.

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- Definition

Aggregate carrying value as of the balance sheet date of the liabilities for deferred compensation arrangements. Represents currently earned compensation under cash arrangements (such as a profit-sharing plan, rabbi trust, and employee contract--excluding equity-based arrangements) that is not actually paid until a later date.

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No definition available.

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- Definition

Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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- Definition

The number of limited partner units outstanding.

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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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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.

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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- Definition

Number of shares issued under share-based payment arrangement.

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- Definition

Number of options vested.

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No definition available.

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Compensation - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Sep. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 shares	Dec. 13, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares available for future awards (in shares)	371,800,000		371,800,000
Number of units redeemed (in shares)	60,312	151,160	419,797	588,160
Number of shares vested and converted (in shares)	900,000		2,400,000
Unrecognized compensation expense related to unvested RSUs \| $	$ 79.0		$ 79.0
Deferred cash compensation expense recognized \| $	0.1	$ 0.2	0.3	$ 0.6
Liability for deferred cash compensation awards \| $	$ 1.2		$ 1.2		$ 1.5
Executives And Non Executives Employees
Share-based Compensation Arrangement by Share-based Payment Award
Limited partners capital account units held by BGC (in shares)	28,200,000		28,200,000
Newmark Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units exchange ratio (in percentage)	0.4545		0.4545
Newmark Holdings, L.P. \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units outstanding (in shares)	10,380,189		10,380,189		4,683,571	219,887
Newmark Holdings, L.P. \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Number of conversion rights granted (in shares)		1,600,000	3,000,000.0	3,300,000
BGC Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units outstanding (in shares)	54,860,495		54,860,495		56,053,701	61,870,969
BGC Holdings, L.P. \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units outstanding (in shares)	9,200,000		9,200,000		9,500,000
Exchangeable partnership units (in shares)	4,500,000		4,500,000		2,900,000
BGC Holdings, L.P. \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Number of conversion rights granted (in shares)	500,000	600,000		1,800,000
NEWMARK Group Inc Parent
Share-based Compensation Arrangement by Share-based Payment Award
Limited partners capital account units held by BGC (in shares)	18,904,604		18,904,604		17,097,639
Limited partnership units outstanding (in shares)	65,731,064		65,731,064		60,800,852	44,733,487
Number of units redeemed (in shares)	25,419	63,594	194,072	208,969
NEWMARK Group Inc Parent \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units outstanding (in shares)	5,200,000		5,200,000		5,300,000
Exchangeable partnership units (in shares)	2,000,000.0		2,000,000.0		1,400,000
Maximum \| Newmark Holdings, L.P. \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period			8 years
Maximum \| NEWMARK Group Inc Parent \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period			7 years
Minimum \| Newmark Holdings, L.P. \| Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period			2 years
Minimum \| NEWMARK Group Inc Parent \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period			3 years
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units exchange ratio (in percentage)	0.9373		0.9373				1
Newmark Equity Plan \| Class A Common Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized to be delivered pursuant to awards granted (in shares)							400,000,000.0
Shares registered to be delivered pursuant to awards granted (in shares)							65,000,000.0
Non Distribution Earning Units
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period			4 years
Unit granted during period (in shares)	1,300,000		3,500,000