Statements Of Changes In Shareholders' Equity (Deficit) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Shareholders' equity (deficit) - beginning of period			$ (1,846,637)	$ (1,748,981)	$ (1,748,981)
Net income	71,611	28,472	88,603	124,490	258,847
Adjustment of redeemable capital Shares to redemption value	(382,245)		(315,115)		(356,503)
Shareholders' equity (deficit) - end of period	$ (2,073,149)		$ (2,073,149)		$ (1,846,637)