XML 34 R71.htm IDEA: XBRL DOCUMENT

Commitments and Contingencies (Details) (USD $)	12 Months Ended
Commitments and Contingencies (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accretion expense related to liabilities for contingent retirement obligations	$ 5,600,000	$ 5,300,000	$ 4,900,000
Asset retirement obligation	68,500,000	63,800,000
Asset retirement obligation future outlay	1,400,000,000
Increase in property tax commitment	3.00%
Letters of credit	10,800,000
Sprint [Member]
Estimated future property tax commitment	15,800,000
Property Taxes [Member] \| Sprint [Member]
Payments for other taxes	$ 15,400,000

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References+ Details

- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References+ Details