Fair Value Measurements (Narrative) (Details) (USD $) In Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Fair Value Measurements [Abstract]
Loss recognized related to valuation adjustments for counterparty default risk	$ 1	$ 1
Valuation adjustments related to derivative contracts	$ 1		$ 2