CONDENSED CONSOLIDATED STATEMENTS OF INCOME UNAUDITED - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues
Total revenues	$ 87,497	$ 85,917
Expenses
Compensation	25,950	25,278
Management fee	4,634	2,164
Distribution costs	10,204	10,913
Other operating expenses	5,453	5,119
Total expenses	46,241	43,474
Operating income	41,256	42,443
Other income (expense)
Net gain from investments	(5,347)	40
Interest and dividend income	492	469
Interest expense	(1,200)	(2,832)
Total other income (expense), net	(6,055)	(2,323)
Income before income taxes	35,201	40,120
Income tax provision	7,940	15,300
Net income attributable to GAMCO Investors, Inc.'s shareholders	$ 27,261	$ 24,820
Net income attributable to GAMCO Investors, Inc.'s shareholders per share:
Basic (in dollars per share)	$ 0.94	$ 0.86
Diluted (in dollars per share)	$ 0.94	$ 0.82
Weighted average shares outstanding:
Basic (in shares)	28,916	28,970
Diluted (in shares)	28,916	31,160
Dividends declared: (in dollars per share)	$ 0.02	$ 0.02
Investment Advisory and Incentive Fees [Member]
Revenues
Total revenues	$ 77,348	$ 74,989
Distribution Fees and Other Income [Member]
Revenues
Total revenues	$ 10,149	$ 10,928