Statements of Changes in Net Assets - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Assets, Beginning of Year	$ 4,904,036,623	$ 5,405,193,851	$ 5,541,130,643
Operations:
Net investment loss	(27,765,547)	(25,335,523)	(28,299,587)
Net realized loss	(55,102,881)	(135,779,475)	(92,120,817)
Net change in unrealized appreciation/depreciation	984,801,878	(311,211,423)	337,891,452
Net increase (decrease) in net assets resulting from operations	901,933,450	(472,326,421)	217,471,048
Capital Share Transactions:
Contributions for Shares issued	1,836,353,140	954,051,929	873,170,446
Distributions for Shares redeemed	(1,101,564,648)	(982,882,736)	(1,226,578,286)
Net increase (decrease) in net assets from capital share transactions	734,788,492	(28,830,807)	(353,407,840)
Increase (decrease) in net assets	1,636,721,942	(501,157,228)	(135,936,792)
Net Assets, End of Year	$ 6,540,758,565	$ 4,904,036,623	$ 5,405,193,851
Shares issued and redeemed
Shares issued (in shares)	120,750,000	64,000,000	55,800,000
Shares redeemed (in shares)	(70,500,000)	(65,900,000)	(75,950,000)
Net increase (decrease) in Shares issued and outstanding (in shares)	50,250,000	(1,900,000)	(20,150,000)