Statements of Changes in Net Assets (Unaudited) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Net Assets, Beginning of Period	$ 12,556,331,670	$ 11,544,738,146	$ 11,548,425,460	$ 10,147,507,137	$ 11,544,738,146	$ 10,147,507,137
Operations:
Net investment loss	(7,621,405)	(7,619,352)	(7,411,485)	(6,856,858)	(15,240,757)	(14,268,343)
Net realized gain	22,410,307	5,847,432	28,860,217	2,561,066	28,257,739	31,421,283
Net change in unrealized appreciation/depreciation	1,012,499,328	114,176,495	(696,835,646)	205,503,998	1,126,675,823	(491,331,648)
Net increase (decrease) in net assets resulting from operations	1,027,288,230	112,404,575	(675,386,914)	201,208,206	1,139,692,805	(474,178,708)
Capital Share Transactions:
Contributions for Shares issued	739,781,522	1,064,902,289	918,575,987	1,237,667,439
Distributions for Shares redeemed	(976,968,626)	(165,713,340)	(992,947,997)	(37,957,322)
Net increase in net assets from capital share transactions	(237,187,104)	899,188,949	(74,372,010)	1,199,710,117
Increase (decrease) in net assets	790,101,126	1,011,593,524	(749,758,924)	1,400,918,323
Net Assets, End of Period	$ 13,346,432,796	$ 12,556,331,670	$ 10,798,666,536	$ 11,548,425,460	$ 13,346,432,796	$ 10,798,666,536
Shares issued and redeemed
Shares issued (in shares)					142,600,000	168,700,000
Shares redeemed (in shares)					(92,900,000)	(83,350,000)
Net increase in Shares issued and outstanding (in shares)					49,700,000	85,350,000