Shareholder Report, Average Annual Return (Details)	6 Months Ended	12 Months Ended	60 Months Ended	120 Months Ended
Shareholder Report, Average Annual Return (Details)	Jun. 30, 2026	Jun. 30, 2026	Jun. 30, 2026	Jun. 30, 2026
C000002886
Average Annual Return [Line Items]
Line Graph and Table Measure Name	The Gabelli ABC Fund - Class I
C000050409
Average Annual Return [Line Items]
Line Graph and Table Measure Name	The Gabelli ABC Fund - Advisor Class
Without Sales Load [Member] \| C000002886
Average Annual Return [Line Items]
Average Annual Return, Percent	3.76%	7.36%	4.63%	3.86%
Without Sales Load [Member] \| C000050409
Average Annual Return [Line Items]
Average Annual Return, Percent	3.61%	7.13%	4.38%	3.61%
S&P 500 Index
Average Annual Return [Line Items]
Average Annual Return, Percent	10.21%	22.32%	13.41%	15.51%
S&P 500 Index
Average Annual Return [Line Items]
Average Annual Return, Percent	10.21%	22.32%	13.41%	15.51%
ICE BofA 3 Month U.S. Treasury Bill Index
Average Annual Return [Line Items]
Average Annual Return, Percent	1.74%	3.84%	3.52%	2.34%
Lipper U.S. Treasury Money-Market Fund Average
Average Annual Return [Line Items]
Average Annual Return, Percent	1.68%	3.65%	3.34%	2.08%
ICE BofA 3 Month U.S. Treasury Bill Index
Average Annual Return [Line Items]
Average Annual Return, Percent	1.74%	3.84%	3.52%	2.34%
Lipper U.S. Treasury Money-Market Fund Average
Average Annual Return [Line Items]
Average Annual Return, Percent	1.68%	3.65%	3.34%	2.08%