CONDENSED CONSOLIDATED STATEMENTS OF INCOME UNAUDITED - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Total revenues	$ 85,788	$ 88,341	$ 260,478	$ 261,858
Expenses
Compensation	17,562	42,919	72,464	97,634
Management fee	1,449	4,935	7,565	9,455
Distribution costs	9,819	11,665	29,875	33,373
Other operating expenses	5,258	5,429	16,245	15,900
Total expenses	34,088	64,948	126,149	156,362
Operating income	51,700	23,393	134,329	105,496
Other income (expense)
Net gain (loss) from investments	(4,328)	2,841	(8,090)	2,867
Interest and dividend income	531	745	1,549	1,765
Interest expense	(759)	(2,688)	(2,881)	(8,269)
Shareholder-designated contribution	(708)	(3,857)	(884)	(3,857)
Total other income/(expense), net	(5,264)	(2,959)	(10,306)	(7,494)
Income before income taxes	46,436	20,434	124,023	98,002
Income tax provision	11,420	3,834	30,164	33,688
Net income attributable to GAMCO Investors, Inc.'s shareholders	$ 35,016	$ 16,600	$ 93,859	$ 64,314
Net income attributable to GAMCO Investors, Inc.'s shareholders per share:
Basic (in dollars per share)	$ 1.22	$ 0.57	$ 3.26	$ 2.22
Diluted (in dollars per share)	$ 1.22	$ 0.55	$ 3.26	$ 2.14
Weighted average shares outstanding:
Basic (in shares)	28,677	28,926	28,789	28,930
Diluted (in shares)	28,739	31,173	28,824	31,144
Dividends declared: (in dollars per share)	$ 0.02	$ 0.02	$ 0.06	$ 0.06
Investment Advisory and Incentive Fees [Member]
Revenues
Total revenues	$ 75,934	$ 77,328	$ 230,616	$ 228,942
Distribution Fees and Other Income [Member]
Revenues
Total revenues	$ 9,854	$ 11,013	$ 29,862	$ 32,916