Significant Accounting Policies (Schedule Of Investment In Platinum) (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) oz	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) oz	Sep. 30, 2017 USD ($) oz	Dec. 31, 2017 USD ($) oz
Significant Accounting Policies [Abstract]
Opening balance (in Ounces) | oz			610,296.7	522,844.9	522,844.9
Creations (in Ounces) | oz			123,497.5		157,717.3
Redemptions (in Ounces) | oz			(123,686.2)		(66,946.0)
Transfers of platinum to pay expenses (in Ounces) | oz			(2,555.6)		(3,319.5)
Closing balance (in Ounces) | oz	607,552.4		607,552.4		610,296.7
Opening balance			$ 565,745	$ 474,220	$ 474,220
Creations			102,889		148,038
Redemptions			(114,917)		(63,632)
Realized loss on platinum distributed for the redemption of Shares	$ (4,049)	$ (4,463)	(28,583)	(16,357)	(17,514)
Transfers of platinum to pay expenses			(2,330)		(3,142)
Realized loss on platinum transferred to pay expenses	(244)	(220)	(619)	(660)	(873)
Change in unrealized (loss) / gain on investment in platinum	(15,334)	$ 4,451	(27,030)	$ 22,469	28,648
Closing balance	$ 495,155		$ 495,155		$ 565,745