Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	Summary of Significant Accounting Policies Recently Adopted Accounting Pronouncements Lease Accounting — Summary of Adoption Impact. Effective January 1, 2019, the Company adopted new guidance on the recognition, measurement, presentation and disclosure of leases (commonly referred to as "ASC 842" or the "new lease standard"). The new lease standard requires lessees to recognize a lease liability, initially measured at the present value of the lease payments for all leases, and a corresponding right-of-use ("ROU") asset. The accounting for lessors remained largely unchanged from previous guidance. Due to the recognition of the lease liability and a corresponding ROU asset, the new lease standard had a material impact on the Company's condensed consolidated balance sheet. Additionally, certain amounts related to our lessee arrangements that were previously reported separately have been de-recognized and reclassified into "Operating lease right-of-use assets" on the Company's condensed consolidated balance sheet. These amounts include (1) the Company's liability related to straight-line expense, formerly referred to as "Deferred ground lease payable" and previously included in "Other accrued liabilities" and "Other long-term liabilities," (2) prepaid rent expense previously included in "Prepaid expenses" and "Long-term prepaid rent and other assets, net," (3) below market leases previously included in "Other intangible assets, net," and (4) above market leases previously included in "Other long-term liabilities." Notwithstanding the material impact to the Company's condensed consolidated balance sheet, the Company's adoption of the new lease standard did not have a material impact on the Company's condensed consolidated statement of operations or statement of cash flows. Additionally, the adoption of this guidance has no impact on the Company's operating practices, cash flows, contractual arrangements, or debt agreements (including compliance with any applicable covenants). Lease Accounting — General. The Company adopted the new lease standard using a modified retrospective approach as of the effective date (i.e., January 1, 2019), without adjusting the comparative periods. The Company's adoption of the new lease standard did not result in a cumulative-effect adjustment being recognized to the opening balance of retained earnings. The new lease standard provides a package of practical expedients, whereby companies can elect not to reassess (1) whether existing contracts contain leases under the new definition of a lease, (2) lease classification for expired or existing leases and (3) whether previously capitalized initial direct costs would qualify for capitalization under ASC 842. The Company elected the package of practical expedients upon adoption and as a result elected not to reassess (1) whether existing contracts contain leases under the new definition of a lease and (2) the classification or lease term of leases that existed prior to January 1, 2019. The Company evaluates whether a contract meets the definition of a lease whenever a contract grants a party the right to control the use of an identified asset for a period of time in exchange for consideration. To the extent the identified asset is able to be shared among multiple parties, the Company has determined that one party does not have control of the identified asset and the contract is not considered a lease. The Company accounts for contracts that do not meet the definition of a lease under other relevant accounting guidance (such as ASC 606 for revenue from contracts with customers). Lease Accounting — Lessee. For its Tower segment, the Company's lessee arrangements primarily consist of ground leases for land under towers. Ground leases for land are specific to each site, generally contain an initial term of five to 10 years and are renewable (and cancelable after a notice period) at the Company's option. The Company also enters into term easements and ground leases in which it prepays the entire term. For its Fiber segment, the Company's lessee arrangements primarily include leases of fiber assets to support the Company's small cells and fiber solutions. The majority of the Company's lease agreements have certain termination rights that provide for cancellation after a notice period and multiple renewal options at the Company's option. The Company includes renewal option periods in its calculation of the estimated lease term when it determines the options are reasonably certain to be exercised. When such renewal options are deemed to be reasonably certain, the estimated lease term determined under ASC 842 will be greater than the non-cancelable term of the contractual arrangement. Although certain renewal periods are included in the estimated lease term, the Company would have the ability to terminate or elect to not renew a particular lease if business conditions warrant such a decision. The Company classifies its lessee arrangements at inception as either operating leases or finance leases. A lease is classified as a finance lease if at least one of the following criteria is met: (1) the lease transfers ownership of the underlying asset to the lessee, (2) the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) the lease term is for a major part of the remaining economic life of the underlying asset, (4) the present value of the sum of the lease payments equals or exceeds substantially all of the fair value of the underlying asset, or (5) the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. A lease is classified as an operating lease if none of the five criteria described above for finance lease classification is met. ROU assets associated with operating leases are included in "Operating lease right-of-use assets" on the Company's condensed consolidated balance sheet. Current and long-term portions of lease liabilities related to operating leases are included in "Current portion of operating lease liabilities" and "Operating lease liabilities" on the Company's condensed consolidated balance sheet. ROU assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's present value of its future lease payments. In assessing its leases and determining its lease liability, the Company was not able to readily determine the rate implicit for its lessee arrangements, and thus has used its incremental borrowing rate on a collateralized basis to determine the present value of the lease payments. The Company's ROU assets are measured as the balance of the lease liability plus any prepaid or accrued lease payments and any unamortized initial direct costs. For both the Towers and Fiber segments, operating lease expenses are recognized on a ratable basis, regardless of whether the payment terms require the Company to make payments annually, quarterly, monthly, or for the entire term in advance. Certain of the Company's ground lease and fiber lease agreements contain fixed escalation clauses (such as fixed dollar or fixed percentage increases) or inflation-based escalation clauses (such as those tied to the change in CPI). If the payment terms include fixed escalator provisions, the effect of such increases is recognized on a straight-line basis. The Company calculates the straight-line expense over the contract's estimated lease term, including any renewal option periods that the Company deems reasonably certain to be exercised. Lease agreements may also contain provisions for a contingent payment based on (1) the revenues derived from the communications infrastructure located on the leased asset, (2) the change in CPI or (3) the usage of the leased asset. The Company's contingent payments are considered variable lease payments and are (1) not included in the initial measurement of the ROU asset or lease liability due to the uncertainty of the payment amount, and (2) recorded as expense in the period such contingencies are resolved. ROU assets associated with finance leases are included in "Property and equipment, net" on the Company's condensed consolidated balance sheet. Lease liabilities associated with finance leases are included in "Current maturities of debt and other obligations" and "Debt and other long-term obligations" on the Company's condensed consolidated balance sheet. For both its Towers and Fiber segments, the Company measures the lease liability for finance leases using the effective interest method. The initial lease liability is increased to reflect interest on the liability and decreased to reflect payments made during the period. Interest on the lease liability is determined each period during the lease term as the amount that results in a constant periodic discount rate on the remaining balance of the liability. The Company measures ROU assets for finance leases on a ratable basis over the applicable lease term. Lease Accounting — Lessor. The Company's lessor arrangements primarily include contracts for dedicated space (including dedicated fiber) on its shared communications infrastructure. The Company classifies its leases at inception as operating, direct financing or sales-type leases. A lease is classified as a sales-type lease if at least one of the following criteria is met: (1) the lease transfers ownership of the underlying asset to the lessee, (2) the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) the lease term is for a major part of the remaining economic life of the underlying asset, (4) the present value of the sum of the lease payments equals or exceeds substantially all of the fair value of the underlying assets or (5) the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. Furthermore, when none of the above criteria is met, a lease is classified as a direct financing lease if both of the following criteria are met: (1) the present value of the of the sum of the lease payments and any residual value guaranteed by the lessee, that is not already reflected in the lease payments, equals or exceeds the fair value of the underlying asset and (2) it is probable that the lessor will collect the lease payments plus any amount necessary to satisfy a residual value guarantee. A lease is classified as an operating lease if it does not qualify as a sales-type or direct financing lease. Currently, the Company classifies all of its lessor arrangements as operating leases. Site rental revenues from the Company’s lessor arrangements are recognized on a straight-line, ratable basis over the fixed, non-cancelable term of the relevant contract, regardless of whether the payments from the tenant are received in equal monthly amounts during the life of a contract. Certain of the Company's contracts contain fixed escalation clauses (such as fixed-dollar or fixed-percentage increases) or inflation-based escalation clauses (such as those tied to the change in CPI). If the payment terms call for fixed elements, such as fixed escalations, upfront payments, or rent-free periods, the rental revenue is recognized on a straight-line basis over the fixed, non-cancelable term of the agreement. When calculating straight-line site rental revenues, the Company considers all fixed elements of tenant contractual escalation provisions. Certain of the Company's arrangements with tenants in its Fiber segment contain both lease and non-lease components. In such circumstances, the Company has determined (1) the timing and pattern of transfer for the lease and non-lease component are the same, and (2) the stand-alone lease component would be classified as an operating lease. As such, the Company has aggregated certain non-lease components with lease components and has determined that the lease components (generally dedicated fiber) represent the predominant component of the arrangement. See notes 3 and 9 for further information. Recent Accounting Pronouncements Not Yet Adopted No new accounting pronouncements issued but not yet adopted are expected to have a material impact on the Company's condensed consolidated financial statements.

Summary of Significant Accounting Policies

Recently Adopted Accounting Pronouncements

Lease Accounting — Summary of Adoption Impact. Effective January 1, 2019, the Company adopted new guidance on the recognition, measurement, presentation and disclosure of leases (commonly referred to as "ASC 842" or the "new lease standard").

The new lease standard requires lessees to recognize a lease liability, initially measured at the present value of the lease payments for all leases, and a corresponding right-of-use ("ROU") asset. The accounting for lessors remained largely unchanged from previous guidance.

Due to the recognition of the lease liability and a corresponding ROU asset, the new lease standard had a material impact on the Company's condensed consolidated balance sheet. Additionally, certain amounts related to our lessee arrangements that were previously reported separately have been de-recognized and reclassified into "Operating lease right-of-use assets" on the Company's condensed consolidated balance sheet. These amounts include (1) the Company's liability related to straight-line expense, formerly referred to as "Deferred ground lease payable" and previously included in "Other accrued liabilities" and "Other long-term liabilities," (2) prepaid rent expense previously included in "Prepaid expenses" and "Long-term prepaid rent and other assets, net," (3) below market leases previously included in "Other intangible assets, net," and (4) above market leases previously included in "Other long-term liabilities."

Notwithstanding the material impact to the Company's condensed consolidated balance sheet, the Company's adoption of the new lease standard did not have a material impact on the Company's condensed consolidated statement of operations or statement of cash flows. Additionally, the adoption of this guidance has no impact on the Company's operating practices, cash flows, contractual arrangements, or debt agreements (including compliance with any applicable covenants).

Lease Accounting — General. The Company adopted the new lease standard using a modified retrospective approach as of the effective date (i.e., January 1, 2019), without adjusting the comparative periods. The Company's adoption of the new lease standard did not result in a cumulative-effect adjustment being recognized to the opening balance of retained earnings. The new lease standard provides a package of practical expedients, whereby companies can elect not to reassess (1) whether existing contracts contain leases under the new definition of a lease, (2) lease classification for expired or existing leases and (3) whether previously capitalized initial direct costs would qualify for capitalization under ASC 842. The Company elected the package of practical expedients upon adoption and as a result elected not to reassess (1) whether existing contracts contain leases under the new definition of a lease and (2) the classification or lease term of leases that existed prior to January 1, 2019.

The Company evaluates whether a contract meets the definition of a lease whenever a contract grants a party the right to control the use of an identified asset for a period of time in exchange for consideration. To the extent the identified asset is able to be shared among multiple parties, the Company has determined that one party does not have control of the identified asset and the contract is not considered a lease. The Company accounts for contracts that do not meet the definition of a lease under other relevant accounting guidance (such as ASC 606 for revenue from contracts with customers).

Lease Accounting — Lessee. For its Tower segment, the Company's lessee arrangements primarily consist of ground leases for land under towers. Ground leases for land are specific to each site, generally contain an initial term of five to 10 years and are renewable (and cancelable after a notice period) at the Company's option. The Company also enters into term easements and ground leases in which it prepays the entire term. For its Fiber segment, the Company's lessee arrangements primarily include leases of fiber assets to support the Company's small cells and fiber solutions.

The majority of the Company's lease agreements have certain termination rights that provide for cancellation after a notice period and multiple renewal options at the Company's option. The Company includes renewal option periods in its calculation of the estimated lease term when it determines the options are reasonably certain to be exercised. When such renewal options are deemed to be reasonably certain, the estimated lease term determined under ASC 842 will be greater than the non-cancelable term of the contractual arrangement. Although certain renewal periods are included in the estimated lease term, the Company would have the ability to terminate or elect to not renew a particular lease if business conditions warrant such a decision.

The Company classifies its lessee arrangements at inception as either operating leases or finance leases. A lease is classified as a finance lease if at least one of the following criteria is met: (1) the lease transfers ownership of the underlying asset to the lessee, (2) the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) the lease term is for a major part of the remaining economic life of the underlying asset, (4) the present value of the sum of the lease payments equals or exceeds substantially all of the fair value of the underlying asset, or (5) the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. A lease is classified as an operating lease if none of the five criteria described above for finance lease classification is met.

ROU assets associated with operating leases are included in "Operating lease right-of-use assets" on the Company's condensed consolidated balance sheet. Current and long-term portions of lease liabilities related to operating leases are included in "Current portion of operating lease liabilities" and "Operating lease liabilities" on the Company's condensed consolidated balance sheet. ROU assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's present value of its future lease payments. In assessing its leases and determining its lease liability, the Company was not able to readily determine the rate implicit for its lessee arrangements, and thus has used its incremental borrowing rate on a collateralized basis to determine the present value of the lease payments. The Company's ROU assets are measured as the balance of the lease liability plus any prepaid or accrued lease payments and any unamortized initial direct costs. For both the Towers and Fiber segments, operating lease expenses are recognized on a ratable basis, regardless of whether the payment terms require the Company to make payments annually, quarterly, monthly, or for the entire term in advance. Certain of the Company's ground lease and fiber lease agreements contain fixed escalation clauses (such as fixed dollar or fixed percentage increases) or inflation-based escalation clauses (such as those tied to the change in CPI). If the payment terms include fixed escalator provisions, the effect of such increases is recognized on a straight-line basis. The Company calculates the straight-line expense over the contract's estimated lease term, including any renewal option periods that the Company deems reasonably certain to be exercised.

Lease agreements may also contain provisions for a contingent payment based on (1) the revenues derived from the communications infrastructure located on the leased asset, (2) the change in CPI or (3) the usage of the leased asset. The Company's contingent payments are considered variable lease payments and are (1) not included in the initial measurement of the ROU asset or lease liability due to the uncertainty of the payment amount, and (2) recorded as expense in the period such contingencies are resolved.

ROU assets associated with finance leases are included in "Property and equipment, net" on the Company's condensed consolidated balance sheet. Lease liabilities associated with finance leases are included in "Current maturities of debt and other obligations" and "Debt and other long-term obligations" on the Company's condensed consolidated balance sheet. For both its Towers and Fiber segments, the Company measures the lease liability for finance leases using the effective interest method. The initial lease liability is increased to reflect interest on the liability and decreased to reflect payments made during the period. Interest on the lease liability is determined each period during the lease term as the amount that results in a constant periodic discount rate on the remaining balance of the liability. The Company measures ROU assets for finance leases on a ratable basis over the applicable lease term.

Lease Accounting — Lessor. The Company's lessor arrangements primarily include contracts for dedicated space (including dedicated fiber) on its shared communications infrastructure. The Company classifies its leases at inception as operating, direct financing or sales-type leases. A lease is classified as a sales-type lease if at least one of the following criteria is met: (1) the lease transfers ownership of the underlying asset to the lessee, (2) the lease grants the lessee an option to purchase the underlying asset that the lessee is reasonably certain to exercise, (3) the lease term is for a major part of the remaining economic life of the underlying asset, (4) the present value of the sum of the lease payments equals or exceeds substantially all of the fair value of the underlying assets or (5) the underlying asset is of such a specialized nature that it is expected to have no alternative use to the lessor at the end of the lease term. Furthermore, when none of the above criteria is met, a lease is classified as a direct financing lease if both of the following criteria are met: (1) the present value of the of the sum of the lease payments and any residual value guaranteed by the lessee, that is not already reflected in the lease payments, equals or exceeds the fair value of the underlying asset and (2) it is probable that the lessor will collect the lease payments plus any amount necessary to satisfy a residual value guarantee. A lease is classified as an operating lease if it does not qualify as a sales-type or direct financing lease. Currently, the Company classifies all of its lessor arrangements as operating leases.

Site rental revenues from the Company’s lessor arrangements are recognized on a straight-line, ratable basis over the fixed, non-cancelable term of the relevant contract, regardless of whether the payments from the tenant are received in equal monthly amounts during the life of a contract. Certain of the Company's contracts contain fixed escalation clauses (such as fixed-dollar or fixed-percentage increases) or inflation-based escalation clauses (such as those tied to the change in CPI). If the payment terms call for fixed elements, such as fixed escalations, upfront payments, or rent-free periods, the rental revenue is recognized on a straight-line basis over the fixed, non-cancelable term of the agreement. When calculating straight-line site rental revenues, the Company considers all fixed elements of tenant contractual escalation provisions.

Certain of the Company's arrangements with tenants in its Fiber segment contain both lease and non-lease components. In such circumstances, the Company has determined (1) the timing and pattern of transfer for the lease and non-lease component are the same, and (2) the stand-alone lease component would be classified as an operating lease. As such, the Company has aggregated certain non-lease components with lease components and has determined that the lease components (generally dedicated fiber) represent the predominant component of the arrangement.

See notes 3 and 9 for further information.

Recent Accounting Pronouncements Not Yet Adopted

No new accounting pronouncements issued but not yet adopted are expected to have a material impact on the Company's condensed consolidated financial statements.