Subsequent Events	9 Months Ended
Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	K. Subsequent Events From October 1, 2015 to November 4, 2015, the Company repurchased 91,740 shares at $57.53 per share. On October 12, 2015, the Board of Directors accelerated the lapse of restrictions on the November 2013 grant of restricted stock awards ("RSAs") effective on October 19, 2015. There were 130,650 RSAs outstanding relating to this grant. As a result of the acceleration, GAMCO will incur a fourth quarter non-cash charge of $5.7 million or $0.13 per diluted share (after management fee and tax benefit). 557,900 RSAs will still remain outstanding after the acceleration of the November 2013 grant. On October 13, 2015 GAMCO announced that it had again adopted a Shareholder Designated Charitable Contribution program for all registered Class A and Class B shareholders. Based on the approximately 21 million shares currently registered in shareholders' names, the total contribution GAMCO is expected to make will be $5.3 million. If all shares outstanding are registered in their shareholders' name at the record date, the total contribution would increase to $6.4 million. On November 2, 2015, GAMCO announced that its Board of Directors had approved the spin-off of Associated Capital Group, Inc. (“AC”), which will include GAMCO’s alternative investment management business, its institutional research services business and financial assets. The distribution is expected to occur at 11:59 p.m. on November 30, 2015 with GAMCO shareholders receiving one share of Associated Capital Group class A common stock for each share of GAMCO class A common stock held on November 12, 2015, the record date, and one share of Associated Capital Group class B common stock for each share of GAMCO class B common stock held on the record date. On November 4, 2015, the Board of Directors declared its regular quarterly dividend of $0.07 per share to all of its shareholders, payable on December 29, 2015 to shareholders of record on December 15, 2015. GAMCO has received a commitment from a related party whereby it will provide to GAMCO a single purpose $100 million line of credit to be drawn upon only to prepay any or all of the outstanding 5.875% Senior Notes (due June 1, 2021). This line of credit will be available for drawdown during a 90 day period to commence on a date to be determined.

K. Subsequent Events

From October 1, 2015 to November 4, 2015, the Company repurchased 91,740 shares at $57.53 per share.

On October 12, 2015, the Board of Directors accelerated the lapse of restrictions on the November 2013 grant of restricted stock awards ("RSAs") effective on October 19, 2015. There were 130,650 RSAs outstanding relating to this grant. As a result of the acceleration, GAMCO will incur a fourth quarter non-cash charge of $5.7 million or $0.13 per diluted share (after management fee and tax benefit). 557,900 RSAs will still remain outstanding after the acceleration of the November 2013 grant.

On October 13, 2015 GAMCO announced that it had again adopted a Shareholder Designated Charitable Contribution program for all registered Class A and Class B shareholders. Based on the approximately 21 million shares currently registered in shareholders' names, the total contribution GAMCO is expected to make will be $5.3 million. If all shares outstanding are registered in their shareholders' name at the record date, the total contribution would increase to $6.4 million.

On November 2, 2015, GAMCO announced that its Board of Directors had approved the spin-off of Associated Capital Group, Inc. (“AC”), which will include GAMCO’s alternative investment management business, its institutional research services business and financial assets. The distribution is expected to occur at 11:59 p.m. on November 30, 2015 with GAMCO shareholders receiving one share of Associated Capital Group class A common stock for each share of GAMCO class A common stock held on November 12, 2015, the record date, and one share of Associated Capital Group class B common stock for each share of GAMCO class B common stock held on the record date.

On November 4, 2015, the Board of Directors declared its regular quarterly dividend of $0.07 per share to all of its shareholders, payable on December 29, 2015 to shareholders of record on December 15, 2015.

GAMCO has received a commitment from a related party whereby it will provide to GAMCO a single purpose $100 million line of credit to be drawn upon only to prepay any or all of the outstanding 5.875% Senior Notes (due June 1, 2021). This line of credit will be available for drawdown during a 90 day period to commence on a date to be determined.