CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY AND NONCONTROLLING INTERESTS (unaudited) - USD ($) $ in Thousands	Total	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 (loss)	Noncontrolling interest
Balance at beginning of period at Dec. 31, 2023			$ 10		$ 31,774		$ 756,468			$ 914	$ 73
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock				$ 0		$ 8,800
Repurchase of Class A non-voting common stock for cancellation				0		(8,384)			$ (1,219)
Share-based expense					9,645
Vested employee share plan awards					(15,580)
Change in redemption value of redeemable noncontrolling interests					264
Net income (loss)	$ 60,518						60,828	[1]			(310)
Dividends paid							(4,985)
Currency translation adjustment	(697)									(697)
Capital addition to noncontrolling interest											237
Balance at end of period at Sep. 30, 2024	$ 837,838	$ 837,838	10		26,519		811,092			217	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.48
Balance at beginning of period at Dec. 31, 2023			10		31,774		756,468			914	73
Balance at end of period at Dec. 31, 2024			10		29,733		819,961			691	0
Balance at beginning of period at Jun. 30, 2024			10		23,365		788,739			(54)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock				0		391
Repurchase of Class A non-voting common stock for cancellation				0		0			(295)
Share-based expense					3,175
Vested employee share plan awards					(412)
Change in redemption value of redeemable noncontrolling interests					0
Net income (loss)	$ 24,508						24,508	[1]			0
Dividends paid							(1,860)
Currency translation adjustment	271									271
Capital addition to noncontrolling interest											0
Balance at end of period at Sep. 30, 2024	$ 837,838	837,838	10		26,519		811,092			217	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.18
Balance at beginning of period at Dec. 31, 2024			10		29,733		819,961			691	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock				0		6,466
Repurchase of Class A non-voting common stock for cancellation				0		(90)			(580)
Share-based expense					9,924
Vested employee share plan awards					(16,310)
Change in redemption value of redeemable noncontrolling interests					0
Net income (loss)	$ 74,041						74,041	[1]			0
Dividends paid							(5,682)
Currency translation adjustment	2,110									2,110
Capital addition to noncontrolling interest											0
Balance at end of period at Sep. 30, 2025	$ 920,274	920,274	10		29,723		887,740			2,801	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.54
Balance at beginning of period at Jun. 30, 2025			10		26,576		867,922			2,350	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock				0		190
Repurchase of Class A non-voting common stock for cancellation				$ 0		$ 0			$ 0
Share-based expense					3,147
Vested employee share plan awards					(190)
Change in redemption value of redeemable noncontrolling interests					0
Net income (loss)	$ 21,712						21,712	[1]			0
Dividends paid							(1,894)
Currency translation adjustment	451									451
Capital addition to noncontrolling interest											0
Balance at end of period at Sep. 30, 2025	$ 920,274	$ 920,274	$ 10		$ 29,723		$ 887,740			$ 2,801	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends paid per share (in dollars per share)	$ 0.18

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