CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY AND REDEEMABLE NONCONTROLLING INTERESTS (unaudited) - USD ($)	Total	Class A Stock	Parent	Common Stock	Common Stock Class A Stock	Additional paid-in capital	Additional paid-in capital Class A Stock	Retained earnings		Retained earnings Class A Stock	Accumulated other comprehensive income	Noncontrolling interest
Balance at beginning of period at Dec. 31, 2022				$ 11,000		$ 28,628,000		$ 764,178,000			$ 1,416,000	$ 722,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock					$ 0		$ 6,040,000
Repurchase of Class A non-voting common stock for cancellation		$ (13,800,000)			(1,000)		(3,898,000)			$ (27,555,000)
Share-based expense						10,054,000
Vested employee share plan awards						(11,892,000)
Capital addition to noncontrolling interest												171,000
Net income	$ 18,676,000							19,079,000	[1]			(403,000)
Change in redemption value of redeemable noncontrolling interests	591,000					(106,000)						(485,000)
Dividends paid								(4,904,000)
Currency translation adjustment	(1,740,000)										(1,740,000)
Balance at end of period at Sep. 30, 2023	779,315,000		$ 779,310,000	10,000		28,826,000		750,798,000			(324,000)	5,000
Balance at beginning of period at Dec. 31, 2022	25,466,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of redeemable noncontrolling interests	(83,000)
Change in redemption value of redeemable noncontrolling interests	591,000					(106,000)						(485,000)
Balance at end of period at Sep. 30, 2023	$ 25,974,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.45
Balance at beginning of period at Dec. 31, 2022				11,000		28,628,000		764,178,000			1,416,000	722,000
Balance at end of period at Dec. 31, 2023	$ 789,239,000			10,000		31,774,000		756,468,000			914,000	73,000
Balance at beginning of period at Dec. 31, 2022	25,466,000
Balance at end of period at Dec. 31, 2023	0
Balance at beginning of period at Jun. 30, 2023				11,000		25,576,000		762,471,000			256,000	109,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock					0		367,000
Repurchase of Class A non-voting common stock for cancellation		(6,500,000)			(1,000)		(211,000)			(23,956,000)
Share-based expense						3,413,000
Vested employee share plan awards						(314,000)
Capital addition to noncontrolling interest												0
Net income	13,779,000							13,861,000	[1]			(82,000)
Change in redemption value of redeemable noncontrolling interests	26,000					(5,000)						(22,000)
Dividends paid								(1,578,000)
Currency translation adjustment	(580,000)										(580,000)
Balance at end of period at Sep. 30, 2023	779,315,000		779,310,000	10,000		28,826,000		750,798,000			(324,000)	5,000
Balance at beginning of period at Jun. 30, 2023	25,948,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of redeemable noncontrolling interests	0
Change in redemption value of redeemable noncontrolling interests	26,000					(5,000)						(22,000)
Balance at end of period at Sep. 30, 2023	$ 25,974,000
Increase (Decrease) in Temporary Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.15
Balance at beginning of period at Dec. 31, 2023	$ 789,239,000			10,000		31,774,000		756,468,000			914,000	73,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock					0		8,800,000
Repurchase of Class A non-voting common stock for cancellation		(9,600,000)			0		(8,384,000)			(1,219,000)
Share-based expense						9,645,000
Vested employee share plan awards						(15,580,000)
Capital addition to noncontrolling interest												237,000
Net income	60,518,000							60,828,000	[1]			(310,000)
Change in redemption value of redeemable noncontrolling interests	0					264,000						0
Dividends paid								(4,985,000)
Currency translation adjustment	(697,000)										(697,000)
Balance at end of period at Sep. 30, 2024	837,838,000		837,838,000	10,000		26,519,000		811,092,000			217,000	0
Balance at beginning of period at Dec. 31, 2023	0
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of redeemable noncontrolling interests	0
Change in redemption value of redeemable noncontrolling interests	0					264,000						0
Balance at end of period at Sep. 30, 2024	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.48
Balance at beginning of period at Jun. 30, 2024				10,000		23,365,000		788,739,000			(54,000)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock					0		391,000
Repurchase of Class A non-voting common stock for cancellation		$ (294,862)			$ 0		$ 0			$ (295,000)
Share-based expense						3,175,000
Vested employee share plan awards						(412,000)
Capital addition to noncontrolling interest												0
Net income	$ 24,508,000							24,508,000	[1]			0
Change in redemption value of redeemable noncontrolling interests	0					0						0
Dividends paid								(1,860,000)
Currency translation adjustment	271,000										271,000
Balance at end of period at Sep. 30, 2024	837,838,000		$ 837,838,000	$ 10,000		26,519,000		$ 811,092,000			$ 217,000	0
Balance at beginning of period at Jun. 30, 2024	0
Increase (Decrease) in Temporary Equity [Roll Forward]
Redemption of redeemable noncontrolling interests	0
Change in redemption value of redeemable noncontrolling interests	0					$ 0						$ 0
Balance at end of period at Sep. 30, 2024	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.18

[1] (1) Attributable to Oppenheimer Holdings Inc.