Fair Value Of Assets And Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified			6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Purchased Put Option [Member] contract	Jun. 30, 2012 Future [Member]	Dec. 31, 2011 Future [Member]
Derivative [Line Items]
Number of derivative contracts			4
Derivative maximum exposure			$ 2.5
Loss on derivative			1.2
Number of futures contracts (as shown)	7	10
Notional value of futures contracts				$ 0.9	$ 1.3