Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009 Guatemala [Member]
Summary Of Significant Accounting Policies [Line Items]
Annual aggregate depreciation allowance	$ 877
Estimated useful lives, minimum, (years)	3
Estimated useful lives, maximum, (years)	30
Asset impairment charges			5
Unbilled revenues	$ 474	$ 633
Investment gains and losses recognized, time period, years	15
Investment gains and losses recognized, time period, years	10
Difference between fair value and expected Market Related Value of plan assets	20.00%