Net Assets Investment Company, Portfolio Turnover C000025170 [Member] The Tax-Exempt Fund of California® - Class A [Member] C000025172 [Member] The Tax-Exempt Fund of California® - Class C [Member] C000189456 [Member] The Tax-Exempt Fund of California® - Class T [Member] C000025173 [Member] The Tax-Exempt Fund of California® - Class F-1 [Member] C000068592 [Member] The Tax-Exempt Fund of California® - Class F-2 [Member] C000180000 [Member] The Tax-Exempt Fund of California® - Class F-3 [Member] Investment Type [Axis] AAA/Aaa [Member] AAA/Aaa [Member] AAAa [Member] AA/Aa [Member] AA [Member] A/A [Member] BBBBaa [Member] BBB/Baa [Member] Below Investment Grade [Member] Below investment grade [Member] Unrated [Member] Short Term Securities And Other Assets Less Liabilities [Member] Short-term securities & other assets less liabilities [Member]