Statements of Changes in Net Assets (Unaudited) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Net Assets, Beginning of Period	$ 7,310,131,020	$ 5,209,802,846
Operations:
Net investment loss	(4,799,173)	(20,312,154)
Net realized gain	2,018,251	25,068,804
Net change in unrealized appreciation/depreciation	546,559,551	303,987,270
Net increase in net assets resulting from operations	543,778,629	308,743,920
Capital Share Transactions:
Contributions for Shares issued	431,456,784	3,784,339,342
Distributions for Shares redeemed	(288,297,575)	(1,992,755,088)
Net increase in net assets from capital share transactions	143,159,209	1,791,584,254
Increase in net assets	686,937,838	2,100,328,174
Net Assets, End of Period	$ 7,997,068,858	$ 7,310,131,020
Shares issued and redeemed
Shares issued (in shares)	36,950,000	314,850,000
Shares redeemed (in shares)	(24,350,000)	(167,950,000)
Net increase in Shares issued and outstanding (in shares)	12,600,000	146,900,000