Tower Sale and Leaseback (Narrative) (Details) - Vertical Bridge Tower Sale [Member] $ in Millions	1 Months Ended
Aug. 31, 2016 USD ($)
Sale Leaseback Transaction [Line Items]
Towers conveyed to VBT	276
Sale Leaseback Transaction, Net Proceeds	$ 90.8
Renewal Options	8
Lessee Leasing Arrangements, Renewal Term	5 years
Annual rent increase	2.00%
Reduction of asset retirement obligation	$ 3.4
Imputed Interest Rate	7.10%
Minimum [Member]
Sale Leaseback Transaction [Line Items]
Lessee Leasing Arrangements, Term of Contract	10 years
Maximum [Member]
Sale Leaseback Transaction [Line Items]
Lessee Leasing Arrangements, Term of Contract	50 years

Property Subject to Sale, Number of Units

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- Definition

Number of renewal options

+ References

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- Definition

Sale Leaseback Transaction, Rent Increase percent

+ References

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- Definition

Amount of increase (decrease) in asset retirement obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

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- Definition

Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

The financing cost related to leases that have been recorded under the deposit method, as a financing or as a capital leases in connection with the transaction involving the sale of property to another party and the lease of the property back to the seller.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Imputed Interest Rate
-URI http://asc.fasb.org/extlink&oid=6515215

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of cash inflow after closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51840-112757

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51831-112757

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=28365400&loc=d3e51843-112757

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