Annual Total Returns - Class Z	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
BNY Mellon AMT-Free Municipal Bond Fund
Prospectus [Line Items]
Annual Return [Percent]	6.49%	(9.41%)	1.60%	4.87%	7.87%	0.74%	5.61%	(0.10%)	3.92%	10.55%
BNY Mellon High Yield Municipal Bond Fund
Prospectus [Line Items]
Annual Return [Percent]	7.25%	(16.79%)	6.13%	2.83%	10.11%	1.64%	13.10%	0.52%	5.24%	12.99%