Cumulative Restructuring And Impairment Costs (Narrative) (Details) (USD $) In Millions, unless otherwise specified	30 Months Ended
	Sep. 30, 2012
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 37
Canadian Operations [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and impairment costs	$ 12