Petroleum Transportation And Storage Securities [Member] Diversified Securities [Member] Master Limited Partnerships [Member] Downstream Other [Member] Upstream [Member] Petroleum Transportation And Storage [Member] Liquefied Natural Gas [Member] Electric LDC And Power [Member] Natural Gas Pipelines [Member] Diversified [Member] C000159803 [Member] Class I C000159801 [Member] Class A Common Stock [Member] Investment Type [Axis] Net Assets Investment Company Portfolio Turnover No Trading Symbol Flag