CONDENSED CONSOLIDATED STATEMENTS OF INCOME UNAUDITED - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Total revenues	$ 87,193	$ 87,600	$ 174,690	$ 173,517
Expenses
Compensation	28,952	29,437	54,902	54,715
Management fee	1,482	2,356	6,116	4,520
Distribution costs	9,852	10,795	20,056	21,708
Other operating expenses	5,534	5,352	10,987	10,471
Total expenses	45,820	47,940	92,061	91,414
Operating income	41,373	39,660	82,629	82,103
Other income (expense)
Net gain (loss) from investments	1,409	(14)	(3,938)	26
Interest and dividend income	526	551	1,018	1,020
Interest expense	(922)	(2,749)	(2,122)	(5,581)
Total other income/(expense), net	1,013	(2,212)	(5,042)	(4,535)
Income before income taxes	42,386	37,448	77,587	77,568
Income tax provision	10,804	14,554	18,744	29,854
Net income attributable to GAMCO Investors, Inc.'s shareholders	$ 31,582	$ 22,894	$ 58,843	$ 47,714
Net income attributable to GAMCO Investors, Inc.'s shareholders per share:
Basic (in dollars per share)	$ 1.10	$ 0.79	$ 2.04	$ 1.65
Diluted (in dollars per share)	$ 1.10	$ 0.76	$ 2.04	$ 1.58
Weighted average shares outstanding:
Basic (in shares)	28,777	28,896	28,846	28,933
Diluted (in shares)	28,819	31,100	28,867	31,130
Dividends declared: (in dollars per share)	$ 0.02	$ 0.02	$ 0.04	$ 0.04
Investment Advisory and Incentive Fees [Member]
Revenues
Total revenues	$ 77,334	$ 76,625	$ 154,682	$ 151,614
Distribution Fees and Other Income [Member]
Revenues
Total revenues	$ 9,859	$ 10,975	$ 20,008	$ 21,903