Related Party Transactions - Additional Information (Detail) - USD ($)																						1 Months Ended					3 Months Ended								9 Months Ended		12 Months Ended
	Sep. 08, 2017	Apr. 21, 2017	Apr. 01, 2017	Dec. 14, 2016	Nov. 16, 2016	Nov. 11, 2016	Nov. 10, 2016	Nov. 07, 2016	Nov. 04, 2016	Oct. 25, 2016	Sep. 30, 2016	Aug. 16, 2016	May 27, 2016	Mar. 09, 2016	Feb. 28, 2016	Feb. 24, 2016	Feb. 23, 2016	Feb. 09, 2016	Jun. 05, 2015	Mar. 11, 2015	Oct. 29, 2013	Sep. 30, 2017	Aug. 31, 2017	Jul. 31, 2017	Feb. 28, 2017	Jan. 31, 2017	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Aug. 04, 2016	Jul. 31, 2016	Oct. 27, 2015	Jun. 23, 2015	Aug. 31, 2013
Related Party Transactions [Abstract]
Recognized related party revenues																														$ 7,173,000				$ 6,354,000	$ 20,129,000	$ 19,086,000
Equity method investments																						$ 134,905,000								134,905,000			$ 30,844,000		134,905,000		$ 30,844,000
Equity investment																																		0	101,623,000	1,112,000
Repurchase agreements																						1,803,000								1,803,000					1,803,000
Commissions																														582,106,000				492,808,000	1,704,998,000	1,465,293,000
Short-term borrowings																						6,313,000								6,313,000					6,313,000
Interest expense																														24,425,000				18,831,000	69,678,000	53,770,000
Principal sum of loan due from related parties																						7,410,000								7,410,000			6,956,000		7,410,000		6,956,000
Reverse purchase agreement outstanding																						0								0			54,659,000		0		54,659,000
Payables to Cantor related to open derivative contracts																						40,629,000								40,629,000			30,475,000		40,629,000		30,475,000
Employee loans																						$ 311,040,000								311,040,000			269,773,000		311,040,000		269,773,000
Interest income																														11,726,000				8,012,000	$ 40,909,000	24,332,000
Repurchase of Class A common stock, shares																						219,238	56,827	19,806							397,539	552,955			1,246,365
Average price per share of common stock repurchased																						$ 13.56	$ 12.95	$ 12.99							$ 11.25	$ 11.07			$ 11.68
Aggregate proceeds from issuance of common stock																																				15,280,000
Securities loaned																						$ 135,070,000								135,070,000			0		$ 135,070,000		0
Related party service fee																					10.00%
Professional and consulting fees																														24,486,000				17,624,000	69,047,000	50,032,000
Payments of referrals for leasing or other services																														4,380,000				5,323,000	16,389,000	15,460,000
Total consideration transferred																																			1,000,000,000		139,000,000
Outstanding advances																						0								0					0
Loan origination related fees and sales premiums, net																														19,772,000				23,372,000	66,673,000	48,122,000
Servicing fees																														29,057,000				$ 22,502,000	$ 80,729,000	$ 62,199,000
Limited partnership units exchange ratio																																			1
Redemption of limited partnership units																0
Employee stock option exercised, shares																																			0
Employee stock option exercise price per share																																			$ 0
Repurchases value of shares																						$ 301,236,000								$ 301,236,000			$ 288,743,000		$ 301,236,000		$ 288,743,000
Share Price																										$ 10.23
Redemptions, Number of Units																														1,675,330	1,908,867	2,927,758			6,511,955
Average price for redemption of limited partnership units																														$ 12.97				$ 8.90	$ 11.40	$ 8.87
Partnership Units [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares								110,000
Percentage of units proportion								55.00%
Treasury Stock, Retired, Cost Method, Amount								$ 952,600
PPSUs [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares								90,000
Average price per share of common stock repurchased								$ 8.60
Percentage of units proportion								45.00%
Treasury Stock, Retired, Cost Method, Amount								$ 773,599
New Class Of Partnership Units [Member]
Related Party Transactions [Abstract]
Gross Revenues Required For Compensation Approval																										$ 5,000,000
BPF [Member]
Related Party Transactions [Abstract]
Total consideration transferred	$ 875,000,000
Business acquistion price paid in units	$ 3,200,000
Business acquisition date	Sep. 08, 2017
Business acquisition, transaction agreement date	Jul. 17, 2017
Net assets exceeded	$ 508,600,000
Gains from Mortgage Banking Activities, Net [Member]
Related Party Transactions [Abstract]
Broker fees and commissions																														$ 300,000				$ 100,000	$ 700,000	$ 1,000,000
5.125% Senior Notes [Member]
Related Party Transactions [Abstract]
Principal amount of debt component													$ 300,000,000
Stated interest rate													5.125%									5.125%								5.125%			5.125%		5.125%		5.125%
Mr. Lutnick [Member]
Related Party Transactions [Abstract]
Grant of new class of partnership units																1,500,000
Partnership units non-exchangeable shares granted															2,127,648
Shares held by executive officers															235,357
Non exchangeable partnership units granted																										325,000
New Class Of Partnership Units Surrendered																										325,000
New Partnership Units																																					2,375,000
Non-exchangeable Partnership Unit																										1,710,000
Non-exchangeable Partnership Unit																										665,000
Non exchangeable partnership units granted																										1,661,600
New Class Of Partnership Units Surrendered																										1,661,600
Aggregate Non Exchangeable Partnership Units Surrendered																										1,986,600
Mr. Lutnick [Member] | Partnership Units [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																750,000
Mr. Lutnick [Member] | PPSUs [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																291,667
Mr. Lynn [Member]
Related Party Transactions [Abstract]
Average price per share of common stock repurchased																										$ 11.07
Grant of new class of partnership units																2,000,000
Shares held by executive officers																										167,654
Determination price																										$ 6.51
Non exchangeable partnership units exchanged to limited partner unit				250,000
New Partnership Units																																					750,000
Non-exchangeable Partnership Unit																										540,000
Non-exchangeable Partnership Unit																										210,000
Non-exchangeable LPU's redeemed, value																										$ 1,958,641
Non-exchangeable PLPUs redeemed, value																										$ 455,993
Mr. Lynn [Member] | Limited Partnership Units [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																621,429
Non exchangeable partnership units granted				3,500,000
Redemptions, Number of Units																										0
Mr. Lynn [Member] | PLPUs [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																241,667
Redemptions, Number of Units																										0
Mr. Lynn [Member] | New Class Of Partnership Units [Member]
Related Party Transactions [Abstract]
Non exchangeable partnership units granted				1,000,000
Mr. Lynn [Member] | Redeemed Price One [Member]
Related Party Transactions [Abstract]
Redemption of limited partnership units																										25,156
Mr. Lynn [Member] | Redeemed Price Two [Member]
Related Party Transactions [Abstract]
Redemption of limited partnership units																										180,115
Mr. Lynn [Member] | Preferred Limited Partnership Units Determination Price Five [Member]
Related Party Transactions [Abstract]
Non-exchangeable PLPUs redeemed																										70,045
Mr. Lynn [Member] | Redeemed Price Three [Member]
Related Party Transactions [Abstract]
Redemption of limited partnership units																										9,480
Mr. Lynn [Member] | Preferred Limited Partnership Units Determination Price Six [Member]
Related Party Transactions [Abstract]
Non-exchangeable PLPUs redeemed																										3,687
Mr. Merkel [Member]
Related Party Transactions [Abstract]
Grant of new class of partnership units																1,000,000
Non exchangeable partnership units granted								200,000
Target revenue to be achieved to grant non exchangeable partnership units																																$ 25,000,000	$ 25,000,000
New Class Of Partnership Units Surrendered								1,714,826
Mr. Merkel [Member] | Scenario, Forecast [Member]
Related Party Transactions [Abstract]
Non exchangeable partnership units granted																											1,000,000
Target revenue to be achieved to grant non exchangeable partnership units																											$ 25,000,000	$ 25,000,000	$ 25,000,000
Mr. Merkel [Member] | Partnership Units [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																114,583
Redemption of limited partnership units																									110,000
Exchange Right Issued								110,000
Share Granted For Exchange Rights																									110,000
Share redemption amount																									$ 1,216,911
Mr. Merkel [Member] | PPSUs [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																93,750
Redemption of limited partnership units																									90,000
Exchange Right Issued								90,000
Share Granted For Exchange Rights																									90,000
Share redemption amount																									$ 847,033
Determination price																									$ 9.41
Mr. Windeatt [Member]
Related Party Transactions [Abstract]
Grant of new class of partnership units																75,000										400,000
Redemption of limited partnership units																										46,469
New Partnership Units																																					18,750
Non-exchangeable Partnership Unit																										13,500
Non-exchangeable Partnership Unit																										5,250
Limited Partnership Unites Granted																										100,000
New Partnership Units Exchanged To Limited Partnership Unit																										100,000
Redemptions, Number of Units																										0
Non-exchangeable LPU's redeemed, value																										$ 505,322
Non-exchangeable PLPUs redeemed																										14,866
Non-exchangeable PLPUs redeemed, value																										$ 96,778
Average price for redemption of limited partnership units																										$ 10.87
Non-exchangeable PLPUs redeemed at determination price																										3,206
Non-exchangeable PLPUs redeemed at determination price, value																										$ 25,103
Mr. Windeatt [Member] | Limited Partnership Units [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																105,188
Mr. Windeatt [Member] | PLPUs [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																40,906
Mr. Windeatt [Member] | Preferred Limited Partnership Units Determination Price One [Member]
Related Party Transactions [Abstract]
Determination price																										$ 6.51
Non-exchangeable PLPUs redeemed																										782
Mr. Windeatt [Member] | Preferred Limited Partnership Units Determination Price Two [Member]
Related Party Transactions [Abstract]
Determination price																										$ 7.83
Non-exchangeable PLPUs redeemed																										347
Mr. Windeatt [Member] | Limited Partnership [Member]
Related Party Transactions [Abstract]
Redemption of limited partnership units																										2,902
Partnership N [Member]
Related Party Transactions [Abstract]
Conversion percentage of new partnership units																25.00%
Mr. Sadler [Member] | Limited Partnership Units [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																55,688
Mr. Sadler [Member] | PLPUs [Member]
Related Party Transactions [Abstract]
Partnership units non-exchangeable shares granted																21,656
Minimum [Member]
Related Party Transactions [Abstract]
Minimum gross revenue required				$ 5,000,000
Class A Common Stock [Member]
Related Party Transactions [Abstract]
Convertible Notes, shares																																					6,909
Repurchase of Class A common stock, shares																														295,871				1,341,947	1,246,365	9,326,182	10,823,942
Average price per share of common stock repurchased																$ 8.40														$ 13.41				$ 8.90	$ 11.68	$ 8.77
Issuance of Class A common stock (net of costs), shares																																			45,490		2,004,533
Common stock, shares issued																						301,294,000								301,294,000			292,549,000		301,294,000		292,549,000
Cantor purchase of Cantor units from BGC Holdings upon redemption of founding/working partner units and subsequent repurchases by BGC Holdings, units																																					624,762
Shares held by executive officers																612,958
Class A Common Stock [Member] | Mr. Lutnick [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares												36,405
Average price per share of common stock repurchased												$ 8.77
Employee stock option exercised, shares						800,000								250,000
Employee stock option exercise price per share						$ 8.80								$ 8.42
Number of shares issued as a result of stock option exercise						51,064								17,403
Repurchases value of shares																																								$ 350,000
Class A Common Stock [Member] | Mr. Lynn [Member]
Related Party Transactions [Abstract]
Shares held by executive officers																431,782
Partnership units received by related parties																120,000
Class A Common Stock [Member] | Mr. Merkel [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares											16,634					4,621
Average price per share of common stock repurchased											$ 8.75
Shares held by executive officers																150,382
Class A Common Stock [Member] | Mr. Merkel [Member] | Partnership Units [Member]
Related Party Transactions [Abstract]
Percentage difference between purchase price of partnership unit and average price of common stock																									2.00%
Class A Common Stock [Member] | Mr. Sadler [Member]
Related Party Transactions [Abstract]
Shares held by executive officers																30,794
Partnership units received by related parties																64,787
Class A Common Stock [Member] | Trusts For Benefit of Merkel's Immediate Family [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares											4,131
Class A Common Stock [Member] | Mr. Dalton [Member]
Related Party Transactions [Abstract]
Employee stock option exercised, shares							7,534
Employee stock option exercise price per share							$ 8.87
Class B Common Stock [Member]
Related Party Transactions [Abstract]
Issuance of Class A common stock (net of costs), shares																														0				0	0	0
Common stock, shares issued																						34,848,000								34,848,000			34,848,000		34,848,000		34,848,000
CF Real Estate Finance Holdings, L.P. [Member]
Related Party Transactions [Abstract]
Equity method investments	100,000,000
Lucera [Member] | Class B Units
Related Party Transactions [Abstract]
Purchase of units										9,000
Percentage of outstanding common stock owned by parent									100.00%
Aqua [Member]
Related Party Transactions [Abstract]
Equity investment																														$ 700,000					$ 1,300,000	$ 1,100,000
Principal sum of loan due from related parties																						$ 980,000								$ 980,000					$ 980,000
Increase in authorization amount for loans and investments, other credit support arrangements																																									$ 4,000,000
Authorization amount for loans and investments, other credit support arrangements																																									$ 16,200,000
Percentage of ownership interest																						49.00%								49.00%					49.00%
Maturity date of subordinated loan																																			Sep. 01, 2018
Loan Receivable, Description of Variable Rate Basis																																			three month LIBOR plus 600 basis points
Loan Receivable, Basis Spread on Variable Rate																						6.00%								6.00%					6.00%
Cantor and ELX [Member]
Related Party Transactions [Abstract]
Cantor's share of net profit in Tower Bridge																														$ 900,000				$ 1,400,000	$ 1,000,000	1,900,000
April 2017 Sales Agreement | Class A Common Stock [Member]
Related Party Transactions [Abstract]
Common stock, shares issued																						0								0					0
Loan Referral Agreement [Member] | Gains from Mortgage Banking Activities, Net [Member]
Related Party Transactions [Abstract]
Revenue from loan referral agreement																														$ 2,800,000				200,000	$ 3,300,000	5,300,000
Cantor [Member]
Related Party Transactions [Abstract]
Mark-up cost of services																																			7.50%
Company ownership of Tower Bridge																																			52.00%
Noncontrolling interest																						48.00%								48.00%					48.00%
Repurchase agreements																						$ 1,800,000								$ 1,800,000					$ 1,800,000
Recognition of share of foreign exchange gains (losses)																														46,000				684,000	(2,800,000)	(106,000)
Commissions																														67,000				36,000	198,000	116,000
Investment in asset-backed commercial paper program																						0								0			$ 0		0		$ 0
Investment authorization in asset-backed commercial paper program																																											$ 350,000,000
Maximum revolving credit		$ 150,000,000
Principal sum of loan due from related parties		$ 150,000,000
Line of credit facility, outstanding amount	150,000,000																					0								0					0
Credit agreement maturity date		Apr. 20, 2018
Interest income from affiliate																														1,300,000					2,600,000
Reverse purchase agreement outstanding																						$ 0								0			54,700,000		0		54,700,000
Professional and consulting fees																														$ 0				0	$ 0	0
Founding partner units remaining																						991,182								991,182					991,182
Cantor [Member] | Audit Committee [Member]
Related Party Transactions [Abstract]
Development expenses																																			$ 1,200,000
Cantor [Member] | Revolving Credit Facility [Member]
Related Party Transactions [Abstract]
Debt Instrument, description																																			The outstanding balances would bear interest at the higher of the borrower’s or the lender’s short-term borrowing rate then in effect, plus 1%.
Cantor [Member] | Maximum [Member] | Audit Committee [Member]
Related Party Transactions [Abstract]
Development expenses																		$ 1,400,000
Cantor [Member] | Maximum [Member] | Revolving Credit Facility [Member]
Related Party Transactions [Abstract]
Principal amount of debt component																																										$ 150,000,000
Cantor [Member] | Class A Common Stock [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares																	5,000,000
Average price per share of common stock repurchased																	$ 8.72
Cantor [Member] | Lucera [Member]
Related Party Transactions [Abstract]
Recognized related party revenues																														$ 300,000				600,000	$ 1,000,000	2,400,000
Cantor [Member] | Lucera [Member] | Class B Units
Related Party Transactions [Abstract]
Equity investment									$ 24,200,000
Post-closing adjustment									$ 4,800,000
Cantor [Member] | Aqua [Member]
Related Party Transactions [Abstract]
Investment ownership percentage																						51.00%								51.00%					51.00%
Cantor and ELX [Member]
Related Party Transactions [Abstract]
Recognized related party revenues																														$ 7,200,000				6,400,000	$ 20,100,000	19,100,000
Service charges																														13,900,000				12,800,000	42,800,000	35,800,000
Compensation to leased employees																														9,500,000				7,500,000	$ 26,400,000	20,400,000
CF Group Management, Inc. [Member]
Related Party Transactions [Abstract]
Number of shares, right to exchange from Class A to Class B common stock																			34,649,693
Cantor Rights to Purchase Exchangeable Units [Member]
Related Party Transactions [Abstract]
Cantor purchase of Cantor units from BGC Holdings upon redemption of founding/working partner units and subsequent repurchases by BGC Holdings, units								624,762
Aggregate exchangeable limited partnership units purchased								141,523
Aggregate consideration amount								$ 560,190
Number of non-exchangeable founding/working partner units redeemed								141,523
Aggregate consideration of non-exchangeable founding/working partner units redeemed								$ 560,190
Founding partner units remaining								548,259
Cantor Rights to Purchase Exchangeable Units [Member] | Exchange Rights [Member]
Related Party Transactions [Abstract]
Aggregate exchangeable limited partnership units purchased								483,239
Aggregate consideration amount								$ 1,796,367
Cantor Rights to Purchase Exchangeable Units [Member] | Maximum [Member]
Related Party Transactions [Abstract]
Number of shares, right to exchange from Class A to Class B common stock																																			34,649,693
Cantor and CFGM [Member] | Class A Common Stock [Member]
Related Party Transactions [Abstract]
Convertible Notes, shares																																			14,676,743
Cantor and CFGM [Member] | Class B Common Stock [Member]
Related Party Transactions [Abstract]
Number of shares, right to exchange from Class A to Class B common stock																																			34,649,693
Cantor and Freedom International Brokerage [Member]
Related Party Transactions [Abstract]
Receivables from Freedom International Brokerage																						$ 1,300,000								1,300,000			1,300,000		$ 1,300,000		1,300,000
Receivables from Cantor related to open derivative contracts																						3,100,000								3,100,000			3,000,000		3,100,000		3,000,000
Payables to Cantor related to open derivative contracts																						1,800,000								1,800,000			1,000,000		1,800,000		1,000,000
Employee Loans [Member]
Related Party Transactions [Abstract]
Employee loans																						311,000,000								311,000,000			269,800,000		311,000,000		269,800,000
Compensation expense related to employee loans																														26,000,000				24,200,000	43,200,000	46,000,000
Interest income																														1,700,000				1,600,000	4,800,000	4,300,000
CF & Co [Member]
Related Party Transactions [Abstract]
Repurchase agreements																						1,800,000								1,800,000			0		1,800,000		0
Securities loaned																						135,100,000								135,100,000			0		135,100,000		0
Guarantee fees																														31,300				$ 31,300	93,800	$ 93,800
CF & Co [Member] | 5.125% Senior Notes [Member] | Underwriting Fees
Related Party Transactions [Abstract]
Underwriting fees													$ 500,000
Purchased senior notes																						15,000,000								15,000,000					15,000,000
CF & Co [Member] | Securities Financing Transaction, Fair Value
Related Party Transactions [Abstract]
Securities loaned																						$ 135,900,000								$ 135,900,000					$ 135,900,000
CF & Co [Member] | Maximum [Member]
Related Party Transactions [Abstract]
Stated interest rate																						2.00%								2.00%					2.00%
CF & Co [Member] | Minimum [Member]
Related Party Transactions [Abstract]
Stated interest rate																						1.30%								1.30%					1.30%
CF & Co [Member] | November 2014 Sales Agreement [Member]
Related Party Transactions [Abstract]
Issuance of Class A common stock (net of costs), shares																														1,100,000				2,300,000	5,400,000	6,000,000
Aggregate proceeds from issuance of common stock																														$ 15,100,000				$ 20,700,000	$ 62,900,000	$ 54,400,000
Weighted-average price per share																														$ 13.24				$ 9.05	$ 11.62	$ 9.12
Related party expenses																														$ 300,000				$ 400,000	$ 1,300,000	$ 1,100,000
Castle Oak | 5.125% Senior Notes [Member] | Underwriting Fees
Related Party Transactions [Abstract]
Underwriting fees													$ 18,000
CCRE [Member]
Related Party Transactions [Abstract]
Recognized related party revenues																														14,000				600,000	100,000	700,000
Payments of referrals for leasing or other services																														0				0	0	0
CCRE [Member] | Note Receivable/Payable [Member]
Related Party Transactions [Abstract]
Interest income from affiliate																														500,000				0	700,000	100,000
Outstanding advances																																	690,000,000				690,000,000
Interest expense																														25,000				1,200,000	2,500,000	1,400,000
CCRE [Member] | One Month LIBOR [Member] | Note Receivable/Payable [Member]
Related Party Transactions [Abstract]
Interest rate																				1.00%
CCRE [Member] | Primary Servicing Rights [Member]
Related Party Transactions [Abstract]
Servicing rights of loans originated																						$ 300,000,000								300,000,000			2,800,000,000		300,000,000		2,800,000,000
Purchase of loans originated																																			600,000		3,900,000
Loan origination related fees and sales premiums, net																														0
Servicing fees																														900,000				$ 900,000	$ 2,800,000	$ 2,700,000
Cantor and CCRE and Cantor Commercial Real Estate Sponsor, L.P. [Member] | BPF [Member]
Related Party Transactions [Abstract]
Transaction agreement, distribution	69,800,000
Net assets exceeded	$ 508,600,000
Chief Financial Officer [Member]
Related Party Transactions [Abstract]
Redemption of limited partnership units			17,115
Determination price			$ 11.07
Non-exchangeable LPU's redeemed, value			$ 188,634
Non-exchangeable PLPUs redeemed, value			$ 73,682
Chief Financial Officer [Member] | Limited Partnership Units [Member]
Related Party Transactions [Abstract]
Redemptions, Number of Units			1,849
Chief Financial Officer [Member] | PLPUs [Member]
Related Party Transactions [Abstract]
Redemptions, Number of Units			0
Chief Financial Officer [Member] | Preferred Limited Partnership Units Determination Price Three [Member]
Related Party Transactions [Abstract]
Non-exchangeable PLPUs redeemed			6,656
Chief Financial Officer [Member] | Preferred Limited Partnership Units Determination Price Four [Member]
Related Party Transactions [Abstract]
Non-exchangeable PLPUs redeemed			719
Relief Fund [Member]
Related Party Transactions [Abstract]
Interest-free loan to related party																																						$ 1,000,000
Promissory note from related party																																							$ 1,000,000
Promissory note repayment date																																			Aug. 04, 2016
Relief Fund [Member] | Accounts Payable, Accrued and Other Liabilities [Member]
Related Party Transactions [Abstract]
Charitable contributions																						$ 30,700,000								$ 30,700,000			$ 30,700,000		$ 30,700,000		$ 30,700,000
Relief Fund [Member] | Other Expenses [Member]
Related Party Transactions [Abstract]
Charitable contributions																																						$ 40,000,000
Cantor Fitzgerald Relief Fund [Member] | Class A Common Stock [Member]
Related Party Transactions [Abstract]
Repurchase of Class A common stock, shares					166,238												970,639
Average price per share of common stock repurchased					$ 9.74												$ 8.72