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Limited partnership units exchange ratio.

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

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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.

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

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

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Number of shares issued under share-based payment arrangement.

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

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Intrinsic value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Number of options vested.

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Compensation - Narrative (Details)		3 Months Ended		6 Months Ended
Compensation - Narrative (Details)	Oct. 18, 2024 shares	Jun. 30, 2026 USD ($) shares	Jun. 30, 2025 USD ($) shares	Jun. 30, 2026 USD ($) shares	Jun. 30, 2025 USD ($) shares	Dec. 31, 2025 USD ($)	Feb. 18, 2025	Oct. 17, 2024 shares	Dec. 13, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units exchange ratio		0.4545		0.4545			0.9279
Compensation expense (benefit) \| $		$ 4,000.0	$ 0	$ 4,000.0	$ 0
Common stock, conversion for each restricted stock unit settled (in shares)				1
Non Distribution Earning Units
Share-based Compensation Arrangement by Share-based Payment Award
Unit granted during period (in shares)		1,900,000	2,800,000	3,700,000	5,700,000
Number of shares vested and converted (in shares)		2,500,000	2,000,000.0	6,300,000	5,300,000
Newmark Holdings, L.P.
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units exchange ratio		0.4545		0.4545
Newmark Holdings, L.P. \| Restricted Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period				8 years
Newmark Holdings Units
Share-based Compensation Arrangement by Share-based Payment Award
Compensation expense (benefit) \| $		$ 63,561,000	$ 57,752,000	$ 129,076,000	$ 131,918,000
Newmark Holdings Units \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation expense \| $		70,100,000		$ 70,100,000		$ 59,700,000
Cost not yet recognized, period for recognition				4 years 1 month 6 days
Newmark Holdings Units \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period				7 years
Shares purchased for award (in shares)				6,800,000
Fair value of non-vested \| $		24,900,000		$ 24,900,000
Unrecognized compensation expense \| $		$ 8,100,000		$ 8,100,000
Cost not yet recognized, period for recognition				2 years 10 months 24 days
Newmark Holdings Units \| Limited Partnership Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award
Award vesting period				7 years
Newmark Holdings Units \| Non Distribution Earning Units \| Limited Partnership Units
Share-based Compensation Arrangement by Share-based Payment Award
Shares purchased for award (in shares)				1,400,000
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units exchange ratio									1
Class A Common Stock \| Newmark Holdings Units
Share-based Compensation Arrangement by Share-based Payment Award
Limited partnership units exchange ratio		0.9260		0.9260
Newmark Equity Plan \| Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized to be delivered pursuant to awards granted (in shares)								500,000,000.0	400,000,000.0
Additional share authorized (in shares)	100,000,000.0
Shares registered to be delivered pursuant to awards granted (in shares)		500,000,000.0		500,000,000.0
Shares purchased for award (in shares)				135,100,000
Shares available for future awards (in shares)		364,900,000		364,900,000