Investments (Details Textual)	12 Months Ended
	Dec. 31, 2019
U.S. Cumulative Dividends Index-Series 2027 [Member]
Investments (Textual)
Description of dividend fund seeks investment	The Dividend Fund seeks investment results that, before fees and expenses, correspond to the performance of the Solactive® U.S. Cumulative Dividends Index—Series 2027 (the “Solactive Dividend Index”) over each calendar year so as to provide Shareholders with returns designed to replicate the dividends on constituent companies of the S&P 500, without exposure to the underlying securities. The Dividend Fund intends primarily to invest its assets in the component instruments of the Solactive Dividend Index, as well as in cash and/or cash equivalents. The component instruments of the Solactive Dividend Index consist of U.S. Treasury Securities (“Treasury Securities”) and long positions in annual futures contracts listed on the Chicago Mercantile Exchange (“CME”) that provide exposure to dividends paid on the S&P 500 constituent companies (“S&P 500 Dividend Futures Contracts”) pro rata for each year of the life of the Dividend Fund.
U.S. Equity Ex-Dividends Index-Series 2027 [Member]
Investments (Textual)
Description of ex-dividend fund seeks investment	The Ex-Dividend Fund seeks investment results that, before fees and expenses, correspond to the performance of the Solactive® U.S. Equity Ex-Dividends Index—Series 2027 (the “Solactive Ex-Dividend Index”). The Ex-Dividend Fund seeks to track the Solactive Ex-Dividend Index so as to provide Shareholders with returns that are equivalent to the performance of 0.25 shares of SPDR S&P 500 exchange-traded fund (“SPY”) less the value of current and future expected ordinary cash dividends to be paid on the S&P 500 constituent companies over the term of the Ex-Dividend Fund. SPY is an exchange-traded fund that seeks to track the S&P 500. The Ex-Dividend Fund seeks to replicate the performance of SPY through owning long positions in quarterly S&P 500 Index futures contracts traded on the CME (“S&P 500 Index Futures Contracts”) rather than shares of SPY. Additionally, the Ex-Dividend Fund intends to track the performance of the Solactive Ex-Dividend Index by selling S&P 500 Dividend Futures Contracts. The Ex-Dividend Fund will also hold Treasury Securities, cash and/or cash equivalents.