Schedule of Investments (Unaudited) (Parenthetical) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
U.S. Equity Cumulative Dividends Fund-Series 2027
Percentages are based on net assets	$ 19,108,998	$ 24,290,529
Total market value of securities pledged as collateral	$ 11,124,992	$ 2,728,628
Percentage of net assets	58.20%	11.20%
U.S. Equity Cumulative Dividends Fund-Series 2027 | Investments
Investment percentage	96.40%	97.10%
Cost, total	$ 18,272,600	$ 23,480,622
U.S. Equity Cumulative Dividends Fund-Series 2027 | U.S. Treasury Obligations
Investment percentage	96.40%	97.10%
Cost, total	$ 18,272,600	$ 23,480,622
U.S. Equity Ex-Dividend Fund-Series 2027
Investment percentage	96.10%	95.90%
Cost, total	$ 25,784,838	$ 25,836,894
Percentages are based on net assets	26,820,873	26,941,802
Total market value of securities pledged as collateral	$ 19,888,060	$ 7,254,010
Percentage of net assets	74.20%	26.90%
U.S. Equity Ex-Dividend Fund-Series 2027 | Investments
Investment percentage	96.10%	95.90%
Cost, total	$ 25,784,838	$ 25,836,894
U.S. Equity Ex-Dividend Fund-Series 2027 | U.S. Treasury Obligations
Investment percentage	96.10%	95.90%
Cost, total	$ 25,784,838	$ 25,836,894
6.125%, 11/15/2027 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security		6.125%
2.250%, 12/31/2023 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.25%	2.25%
2.250%, 11/15/2024 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.25%	2.25%
2.250%, 11/15/2025 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.25%	2.25%
2.125%, 12/31/2022 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.125%	2.125%
2.000%, 12/31/2021 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.00%	2.00%
2.000%, 11/15/2026 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.00%	2.00%
1.750%, 12/31/2020 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	1.75%	1.75%
1.537%, 05/28/2020 | U.S. Equity Ex-Dividend Fund-Series 2027
Coupon rate for this security	1.537%	1.537%
2.250%, 11/15/2027 | U.S. Equity Cumulative Dividends Fund-Series 2027
Coupon rate for this security	2.25%