Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total		Share Capital	Share Capital Class A Stock	Contributed Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Parent	Non-Controlling Interest
Balance at beginning of period at Dec. 31, 2016			$ 59,361		$ 41,765	$ 410,258	$ (681)		$ 2,631
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock				$ 4,225
Repurchase of Class A non-voting common stock for cancellation				(7,464)
Share-based expense					4,112
Vested employee share plan awards					(6,457)
Cumulative-effect adjustment from adoption of new accounting update of employee share-based accounting					425
Net income attributable to Oppenheimer Holdings Inc.	$ 1,623					1,623		$ 1,623
Dividends paid ($0.33 per share)						(4,394)
Dividends received from non-controlling interest						6
Cumulative-effect adjustment from adoption of new accounting update of employee share-based accounting						(314)
Currency translation adjustment	1,953	[1]					1,953
Less net income (loss) attributable to non-controlling interest, net of tax	180							0	180
Dividends paid to non-controlling interest	2,448							0	(2,448)
Distributions Dividends paid to Controlling Interests									(6)
Balance at end of period at Sep. 30, 2017	504,775		56,122		39,845	407,179	1,272	504,418	357
Balance at beginning of period at Dec. 31, 2017	523,911		58,492		36,546	426,930	1,582	523,550	361
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A non-voting common stock				794
Repurchase of Class A non-voting common stock for cancellation				$ 0
Share-based expense					4,647
Vested employee share plan awards					(831)
Cumulative-effect adjustment from adoption of new accounting update of employee share-based accounting					0
Net income attributable to Oppenheimer Holdings Inc.	20,631					20,631		20,631
Dividends paid ($0.33 per share)						(4,373)
Dividends received from non-controlling interest						0
Cumulative-effect adjustment from adoption of new accounting update of employee share-based accounting						0
Currency translation adjustment	(880)	[1]					(880)
Less net income (loss) attributable to non-controlling interest, net of tax	(22)							0	(22)
Dividends paid to non-controlling interest	0								0
Distributions Dividends paid to Controlling Interests									0
Balance at end of period at Sep. 30, 2018	$ 543,877		$ 59,286		$ 40,362	$ 443,188	$ 702	$ 543,538	$ 339

[1] No other comprehensive income (loss) is attributable to non-controlling interests.