Statements of Changes in Net Assets (Unaudited) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Net Assets, Beginning of Period	$ 5,209,803	$ 6,213,387
Operations:
Net investment loss	(4,183)	(15,246)
Net realized gain	7,007	(87,792)
Net change in unrealized appreciation/depreciation	935,096	(659,078)
Net increase (decrease) in net assets resulting from operations	937,920	(762,116)
Capital Share Transactions:
Contributions for Shares issued	1,593,830	830,131
Distributions for Shares redeemed	(332,910)	(1,071,599)
Net increase (decrease) in net assets from capital share transactions	1,260,920	(241,468)
Increase (decrease) in net assets	2,198,840	(1,003,584)
Net Assets, End of Period	$ 7,408,643	$ 5,209,803
Shares issued and redeemed
Shares issued (in shares)	140,950,000	72,050,000
Shares redeemed (in shares)	(28,200,000)	(99,350,000)
Net increase (decrease) in Shares issued and outstanding (in shares)	112,750,000	(27,300,000)