Supplementary Quarterly Financial Data Schedule (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Quarterly Financial Information [Line Items]
Revenue	$ 278,312		$ 278,315	$ 272,796	$ 273,501	$ 289,904		$ 294,620	$ 286,738	$ 272,109	$ 1,102,924		$ 1,143,371		$ 926,609
Operating income	90,834		88,690	84,211	77,773	84,822		88,636	87,670	74,555	341,508		335,683		279,446
Net income including the noncontrolling interests in subsidiaries	131,974	[1]	57,241	54,659	51,027	$ 57,229		58,908	56,418	48,959	294,901		221,514		171,986
Income tax expense (benefit), continuing operations, adjustment of deferred tax (asset) liability	$ 70,400										$ 70,400
Earnings Per Share impact of revaluation of net deferred tax liability	$ 0.70										$ 0.69
Negative impact to EPS as a result of the special dividend						$ (0.02)
Amounts attributable to Federated Investors, Inc.
Net income	$ 131,810	[1]	$ 56,439	$ 53,451	$ 49,641	$ 55,842		$ 54,925	$ 52,709	$ 45,443	$ 291,341	[2]	$ 208,919		$ 169,807
Earnings per common share—Basic and Diluted	$ 1.31	[3]	$ 0.56	$ 0.53	$ 0.49	$ 0.52	[4]	$ 0.54	$ 0.51	$ 0.44	$ 2.87	[5],[6]	$ 2.03	[6]	$ 1.62	[6]
Impact of Voluntary Yield-related Fee Waivers
Revenue	$ 0		$ (10)	$ (144)	$ (4,262)	$ (11,027)		$ (18,030)	$ (21,333)	$ (37,482)	$ (4,400)		$ (87,800)		$ (333,600)
Less: Reduction in Distribution expense	(2)		(1)	99	3,490	7,627		13,797	16,528	27,896	3,600		65,800		240,600
Operating income	(2)		(11)	(45)	(772)	(3,400)		(4,233)	(4,805)	(9,586)	(800)		(22,000)		(93,000)
Less: Reduction in Noncontrolling interest	0		0	0	0	0		0	(208)	208	0		0		7,100
Pre-tax impact	$ (2)		$ (11)	$ (45)	$ (772)	$ (3,400)		$ (4,233)	$ (5,013)	$ (9,378)	$ (800)		$ (22,000)		$ (85,900)
SpecialDividend [Member]
Quarterly Financial Information [Line Items]
Common stock, dividends, per share, cash paid						$ 1.00
QuarterlyDividend [Member]
Quarterly Financial Information [Line Items]
Common stock, dividends, per share, cash paid						$ 0.25

[1] The quarter ended December 31, 2017 includes a $70.4 million reduction to the income tax provision resulting from the revaluation of the net deferred tax liability due to the enactment of the Tax Act, thereby increasing net income.

[2] 2017 includes a $70.4 million reduction to the income tax provision resulting from the revaluation of the net deferred tax liability due to the enactment of the Tax Act, thereby increasing net income.

[3] The quarter ended December 31, 2017 includes a $0.70 increase to earnings per share resulting from the revaluation of the net deferred tax liability due to the enactment of the Tax Act.

[4] For the quarter ended December 31, 2016, Federated paid $1.00 per share as a special cash dividend and a $0.25 per share regular cash dividend. All dividends were considered ordinary dividends for tax purposes. The special dividend negatively impacted fourth quarter 2016 earnings per share by $0.02.

[5] 2017 includes a $0.69 increase to earnings per share resulting from the revaluation of the net deferred tax liability due to the enactment of the Tax Act.

[6] Federated Common Stock excludes unvested restricted stock which are deemed participating securities in accordance with the two-class method of computing earnings per share.