Statements Of Changes In Shareholders' Equity (Deficit) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shareholders' equity (deficit) - beginning of period	$ (1,846,637)	$ (1,748,981)	$ (878,372)
Net income	136,332	258,847	32,297
Adjustment of redeemable capital Shares to redemption value	(622,423)	(356,503)	(902,906)
Shareholders' equity (deficit) - end of period	$ (2,332,728)	$ (1,846,637)	$ (1,748,981)