The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

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+ Details

Basis of Presentation and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue Recognition
Term of IRUs, which are the exclusive right to use a specified amount of capacity or fiber	20 years
Advertising Costs
Advertising expense	$ 189	$ 275	$ 49
Income Taxes
Valuation allowance, primarily related to state NOLs	$ 281
Minimum
Revenue Recognition
Customer relationship period over which revenue is recognized, low end of range	18 months
Accounts Receivable and Allowance for Doubtful Accounts
Period of accounts past due	30 days
Maximum
Revenue Recognition
Customer relationship period over which revenue is recognized, low end of range	10 years