Significant Accounting Policies (Details) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010
Revenue Recognition [Abstract]
Contract measurement period					3 years
Performance fee income			$ 1,000,000		$ 300,000		$ 1,300,000
Computation of basic earnings per share [Abstract]
Net Income for Basic Earnings per Share	614,000		859,000		1,621,000		2,516,000
Basic Weighted-Average Shares Outstanding (in shares)	10,565,406		9,904,187		10,570,247		9,646,298
Basic Earnings per Share (in dollars per share)	$ 0.06		$ 0.09		$ 0.15		$ 0.26
Diluted net income [Abstract]
Non-Controlling Interests	6,392,000		9,741,000		15,070,000		19,081,000
Net Income Attributable to Pzena Investment Management, Inc	614,000		859,000		1,621,000		2,516,000
Diluted Net Income	614,000		859,000		10,032,000		13,390,000
Diluted Net Income Allocated to: [Abstract]
Total Diluted Net Income Attributable to Shareholders	614,000		859,000		10,032,000		13,390,000
Basic Weighted-Average Shares Outstanding (in shares)	10,565,406		9,904,187		10,570,247		9,646,298
Dilutive Effect of Operating Company B Units (in shares)	0		0		54,010,518		54,742,805
Dilutive Effect of Options (in shares)	0		0		463,088		667,194
Dilutive Effect of Phantom Units (in shares)	0		0		105,987		14,415
Dilutive Weighted-Average Shares Outstanding (in shares)	10,565,406		9,904,187		65,149,840		65,070,712
Add: Participating Class B Restricted Units (in shares)	0		0		245,487		0
Total Dilutive Weighted-Average Shares Outstanding (in shares)	10,565,406		9,904,187		65,395,327		65,070,712
Diluted Earnings per Share (in dollars per share)	$ 0.06		$ 0.09		$ 0.15		$ 0.21
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net income per share (in shares)	59,481,989		59,247,364		4,623,446		1,019,476
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	31,890,000		25,196,000		31,890,000		25,196,000		27,801,000	35,083,000	22,054,000	16,381,000
Restricted Cash [Abstract]
Restricted Cash.	1,030,000				1,030,000					1,030,000
Business Segments [Abstract]
Number of Operating Segments					1
Income Taxes [Abstract]
Valuation allowance on deferred tax assets	60,427,000		58,661,000		60,427,000		58,661,000		59,981,000	61,050,000	60,641,000	59,431,000
Property and Equipment [Member] | Minimum [Member]
Property and Equipment [Line Items]
Useful life of property and equipment					3 years
Property and Equipment [Member] | Maximum [Member]
Property and Equipment [Line Items]
Useful life of property and equipment					7 years
Level 1 [Member]
Fair value of instruments [Abstract]
Equity Securities	1,899,000				1,899,000					2,285,000
Investments in Mutual Funds	2,700,000				2,700,000					2,634,000
Total Fair Value	4,599,000				4,599,000					4,919,000
Level 2 [Member]
Fair value of instruments [Abstract]
Equity Securities	0				0					0
Investments in Mutual Funds	0				0					0
Total Fair Value	0				0					0
Level 3 [Member]
Fair value of instruments [Abstract]
Equity Securities	0				0					0
Investments in Mutual Funds	0				0					0
Total Fair Value	0				0					0
Operating Company Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net income per share (in shares)	54,043,981		54,484,796		0		0
Options to Purchase Operating Company Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net income per share (in shares)	3,926,432		3,648,117		3,463,344		989,476
Options to Purchase Shares of Class A Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net income per share (in shares)	971,750		961,750		971,750		0
Phantom Operating Company Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net income per share (in shares)	294,339		152,701		188,352		30,000
Participating Class B Restricted Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net income per share (in shares)	245,487		0		0		0
Common Class A [Member]
Diluted Net Income Allocated to: [Abstract]
Total Diluted Net Income Attributable to Shareholders	614,000		859,000		9,994,000		13,390,000
Participating Class B Restricted Units [Member]
Diluted Net Income Allocated to: [Abstract]
Total Diluted Net Income Attributable to Shareholders	0		0		38,000		0
Pzena International Value Service [Member]
Schedule of Equity Method Investments [Line Items]
Net Assets	1,100,000				1,100,000
Pzena Large Cap Value Fund [Member]
Schedule of Equity Method Investments [Line Items]
Net Assets	900,000				900,000
VIEs that are not consolidated [Member]
Schedule of Equity Method Investments [Line Items]
Net Assets	147,800,000				147,800,000					219,200,000
Pzena Investment Management, LLC [Member]
Diluted net income [Abstract]
Non-Controlling Interests	6,508,000		9,740,000		14,717,000		19,030,000
Less: Assumed Corporate Income Taxes	2,789,000		4,177,000		6,306,000		8,156,000
Assumed After-Tax Income of Pzena Investment Management, LLC	3,719,000		5,563,000		8,411,000		10,874,000
Net Income Attributable to Pzena Investment Management, Inc	614,000		859,000		1,621,000		2,516,000
Diluted Net Income	$ 4,333,000	[1]	$ 6,422,000	[1]	$ 10,032,000	[1]	$ 13,390,000	[1]

[1] Since the assumed incremental income results in an increase per share income for the three months ended June 30, 2012, the assumed effects of the conversion of operating company Class B units.