Earnings Per Share Attributable to Federated Investors, Inc. Shareholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator
Net Income Attributable to Federated Investors, Inc.	$ 61,536	$ 59,608	$ 38,822	$ 60,331	$ 131,810	$ 56,439	$ 53,451	$ 49,641	$ 220,297	$ 291,341	$ 208,919
Less: Total Net Income Available to Participating Unvested Restricted Shareholders									(8,555)	(11,420)	(7,632)
Total Net Income Attributable to Federated Common Stock - Basic									211,742	279,921	201,287
Less: Total Net Income Available to Unvested Restricted Shareholders of a Nonpublic Consolidated Subsidiary									(794)	0	0
Total Net Income Attributable to Federated Common Stock - Diluted									$ 210,948	$ 279,921	$ 201,287
Denominator
Basic Weighted-Average Federated Common Stock (in shares)									96,949	97,411	99,116
Dilutive Potential Shares from Stock Options (in shares)									0	1	1
Diluted Weighted-Average Federated Common Stock (in shares)									96,949	97,412	99,117
Earnings Per Share
Earnings Per Common Share—Basic and Diluted (usd per share)	$ 0.61	$ 0.59	$ 0.38	$ 0.60	$ 1.31	$ 0.56	$ 0.53	$ 0.49	$ 2.18	$ 2.87	$ 2.03
Reduction to income tax provision					$ 70,400					$ 70,400
Earnings per share impact of revaluation of net deferred tax liability (usd per share)					$ 0.70					$ 0.69