Net Assets Investment Company, Portfolio Turnover C000025083 [Member] American High-Income Trust - Class A C000077919 [Member] American High-Income Trust - Class R-6 C000164805 [Member] American High-Income Trust - Class R-5E C000025088 [Member] American High-Income Trust - Class R-5 C000025085 [Member] American High-Income Trust - Class R-2 C000148436 [Member] American High-Income Trust - Class R-2E C000025086 [Member] American High-Income Trust - Class R-3 C000025087 [Member] American High-Income Trust - Class R-4 C000025090 [Member] American High-Income Trust - Class C C000189442 [Member] American High-Income Trust - Class T C000025091 [Member] American High-Income Trust - Class F-1 C000068571 [Member] American High-Income Trust - Class F-2 C000179954 [Member] American High-Income Trust - Class F-3 C000025092 [Member] American High-Income Trust - Class 529-A C000025094 [Member] American High-Income Trust - Class 529-C C000025095 [Member] American High-Income Trust - Class 529-E C000189441 [Member] American High-Income Trust - Class 529-T C000025096 [Member] American High-Income Trust - Class 529-F-1 C000224588 [Member] American High-Income Trust - Class 529-F-2 C000224587 [Member] American High-Income Trust - Class 529-F-3 C000025084 [Member] American High-Income Trust - Class R-1 Investment Type [Axis] U S Corporate Bonds And Notes [Member] U.S. corporate bonds & notes [Member] Corporate Bonds And Notes Of Issuers Outside The US [Member] Corporate bonds & notes of issuers outside the U.S. [Member] Loans [Member] Other Bonds Notes And Debt Instruments [Member] Other bonds, notes & debt instruments [Member] Common Stock [Member] Other Securities [Member] Short Term Securities And Other Assets Less Liabilities [Member] Short-term securities & other assets less liabilities [Member]