Statements Of Changes In Shareholders' Equity (Deficit) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statements Of Changes In Shareholders' Equity (Deficit) [Abstract]
Shareholders' equity (deficit) - beginning of period	$ (1,748,981)	$ (878,372)	$ (448,521)
Net income	258,847	32,297	60,970
Adjustment of redeemable capital Shares to redemption value	(356,503)	(902,906)	(490,821)
Shareholders' equity (deficit) - end of period	$ (1,846,637)	$ (1,748,981)	$ (878,372)