Swiss Franc Deposits - Additional Information (Detail)	3 Months Ended			12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2020 CHF (SFr)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 CHF (SFr)	Mar. 31, 2020 CHF (SFr)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 CHF (SFr)
Cash And Cash Equivalents [Abstract]
Principal deposits	$ 33,393,924	SFr 27,605,719	$ 9,316,175	SFr 46,358,107
Principal redemptions	24,046,323	22,991,844	$ 32,867,039	88,118,747
Withdrawals (to pay expenses)		SFr 392,010		SFr 1,759,836
Deposits, interest bearing	$ 137,884,181				SFr 133,409,839	$ 133,410,414	SFr 129,187,974
Annual nominal rate	(0.75%)				(0.75%)