Statements of Assets and Liabilities (Parenthetical) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Statements of Assets and Liabilities [Abstract]
Investment in platinum at cost	$ 669,168	$ 712,727
Common stock, shares authorized	Unlimited	Unlimited
Common stock, par value	$ 0	$ 0
Common stock, shares issued	6,400,000	6,400,000
Common stock, shares outstanding	6,400,000	6,400,000
Net asset value per share	$ 77.33	$ 88.36