Net Assets Investment Company, Portfolio Turnover C000025125 [Member] American Funds Short-Term Tax-Exempt Bond Fund® - Class A C000189424 [Member] American Funds Short-Term Tax-Exempt Bond Fund® - Class T C000079135 [Member] American Funds Short-Term Tax-Exempt Bond Fund® Class F-1 C000079136 [Member] American Funds Short-Term Tax-Exempt Bond Fund® Class F-2 C000179995 [Member] American Funds Short-Term Tax-Exempt Bond Fund® Class F-3 No Trading Symbol Flag C000186457 [Member] American Funds Short-Term Tax-Exempt Bond Fund® Class R-6 Investment Type [Axis] AAA/Aaa [Member] AA/Aa [Member] A/A [Member] BBB/Baa [Member] Unrated [Member] Short Term Securities And Other Assets Less Liabilities [Member] Short-term securities & other assets less liabilities [Member]