Basis of Presentation (Policies)	9 Months Ended
Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	The accounting policies of Telephone and Data Systems, Inc. (TDS) conform to accounting principles generally accepted in the United States of America (GAAP) as set forth in the Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC). Unless otherwise specified, references to accounting provisions and GAAP in these notes refer to the requirements of the FASB ASC. The consolidated financial statements include the accounts of TDS and subsidiaries in which it has a controlling financial interest, including TDS’ 82%-owned subsidiary, United States Cellular Corporation (U.S. Cellular) and TDS’ wholly-owned subsidiary, TDS Telecommunications LLC (TDS Telecom). In addition, the consolidated financial statements include certain entities in which TDS has a variable interest that require consolidation under GAAP. All material intercompany accounts and transactions have been eliminated. TDS’ business segments reflected in this Quarterly Report on Form 10-Q for the period ended September 30, 2019, are U.S. Cellular, Wireline, and Cable. TDS’ non-reportable other business activities are presented as “Corporate, Eliminations and Other”, which includes the operations of TDS’ wholly-owned hosted and managed services (HMS) subsidiary, which operates under the OneNeck IT Solutions brand, and its wholly-owned subsidiary Suttle-Straus, Inc. (Suttle-Straus). HMS’ and Suttle-Straus’ financial results were not significant to TDS’ operations. All of TDS’ segments operate only in the United States. See Note 13 — Business Segment Information for summary financial information on each business segment.
Basis of Accounting	The unaudited consolidated financial statements included herein have been prepared by TDS pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, TDS believes that the disclosures included herein are adequate to make the information presented not misleading. Certain numbers included herein are rounded to millions for ease of presentation; however, certain calculated amounts and percentages are determined using the unrounded numbers. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in TDS’ Annual Report on Form 10-K (Form 10-K) for the year ended December 31, 2018. The accompanying unaudited consolidated financial statements contain all adjustments (consisting of normal recurring items, unless otherwise disclosed) necessary for the fair statement of TDS’ financial position as of September 30, 2019 and December 31, 2018, its results of operations, comprehensive income and changes in equity for the three and nine months ended September 30, 2019 and 2018, and its cash flows for the nine months ended September 30, 2019 and 2018. These results are not necessarily indicative of the results to be expected for the full year. TDS has not changed its significant accounting and reporting policies from those disclosed in its Form 10-K for the year ended December 31, 2018, except as disclosed in Note 9 — Leases.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted	In June 2016, the FASB issued Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 requires entities to use a new forward-looking, expected loss model to estimate credit losses. It also requires additional disclosure relating to the credit quality of trade and other receivables, including information relating to management’s estimate of credit allowances. TDS is required to adopt ASU 2016-13 on January 1, 2020, using the modified retrospective approach. Early adoption is permitted; however, TDS does not intend to adopt early. The adoption of ASU 2016-13 is not expected to have a significant impact on TDS' financial position or results of operations. In February 2016, the FASB issued Accounting Standards Update 2016-02, Leases and has since amended the standard with Accounting Standards Update 2018-01, Leases: Land Easement Practical Expedient for Transition to Topic 842, Accounting Standards Update 2018-10, Codification Improvements to Topic 842, Leases, Accounting Standards Update 2018-11, Leases: Targeted Improvements, and Accounting Standards Update 2018-20, Leases: Narrow-Scope Improvements for Lessors, collectively referred to as ASC 842. This standard replaces the previous lease accounting standard under ASC 840 - Leases and requires lessees to record a right-of-use (ROU) asset and lease liability for the majority of leases. TDS adopted the provisions of ASC 842 on January 1, 2019, using a modified retrospective method. Under this method, TDS elected to apply the new accounting standard only to the most recent period presented, recognizing the cumulative effect of the accounting change, if any, as an adjustment to the beginning balance of retained earnings. Accordingly, prior periods have not been recast to reflect the new accounting standard. The cumulative effect of applying the provisions of ASC 842 had no material impact on retained earnings.
Revenue from Contract with Customer	As a practical expedient, costs with an amortization period of one year or less are not capitalized.As a practical expedient, revenue related to contracts of less than one year, generally month-to-month contracts, are excluded from these estimates. TDS has certain contracts at U.S. Cellular and TDS Telecom in which it bills an amount equal to a fixed per-unit price multiplied by a variable quantity (e.g., certain roaming agreements with other carriers). Because TDS invoices for such items in an amount that corresponds directly with the value of the performance completed to date, TDS may recognize revenue in that amount. As a practical expedient, these contracts are excluded from the estimate of future revenues expected to be recognized related to performance obligations that are unsatisfied as of the end of a reporting period.
Lessee Agreements	A lease is generally present in a contract if the lessee controls the use of identified property, plant or equipment for a period of time in exchange for consideration. Nearly all of TDS’ leases are classified as operating leases, although it does have a small number of finance leases. TDS’ most significant leases are for land and tower spaces, network facilities, retail spaces, and offices. TDS has agreements with both lease and nonlease components, which are accounted for separately. As part of the present value calculation for the lease liabilities, TDS uses an incremental borrowing rate as the rates implicit in the leases are not readily determinable. The incremental borrowing rates used for lease accounting are based on TDS' unsecured rates, adjusted to approximate the rates at which TDS would be required to borrow on a collateralized basis over a term similar to the recognized lease term. TDS applies the incremental borrowing rates to lease components using a portfolio approach based upon the length of the lease term and the reporting entity in which the lease resides. The cost of nonlease components in TDS’ lease portfolio (e.g., utilities and common area maintenance) are not typically predetermined at lease commencement and are expensed as incurred at their relative standalone price. Variable lease expense occurs when, subsequent to the lease commencement, lease payments are made that were not originally included in the lease liability calculation. TDS’ variable lease payments are primarily a result of leases with escalations that are tied to an index. The incremental changes due to the index changes are recorded as variable lease expense and are not included in the ROU assets or lease liabilities. Lease term recognition determines the periods to which expense is allocated and also has a significant impact on the ROU asset and lease liability calculations. Many of TDS’ leases include renewal and early termination options. At lease commencement, the lease terms include options to extend the lease when TDS is reasonably certain that it will exercise the options. The lease terms do not include early termination options unless TDS is reasonably certain to exercise the options. Certain asset classes have similar lease characteristics; therefore, TDS has applied the portfolio approach for lease term recognition for its tower space, retail, and certain ground lease asset classes.
Lessor Agreements	TDS’ most significant lessor leases are for tower space and colocation space. All of TDS’ lessor leases are classified as operating leases. A lease is generally present in a contract if the lessee controls the use of identified property, plant, or equipment for a period of time in exchange for consideration. TDS’ lessor agreements with lease and nonlease components are generally accounted for separately; however, certain service agreements with insignificant lease components are accounted for as nonlease transactions. Lease term recognition determines the periods to which revenue is allocated over the term of the lease. Many of TDS’ leases include renewal and early termination options. At lease commencement, lease terms include options to extend the lease when TDS is reasonably certain that lessees will exercise the options. Lease terms would not include periods after the date of a termination option that lessees are reasonably certain to exercise. Variable lease income occurs when, subsequent to the lease commencement, lease payments are received that were not originally included in the lease receivable calculation. TDS’ variable lease income is primarily a result of leases with escalations that are tied to an index. The incremental increases due to the index changes are recorded as variable lease income.
Variable Interest Entities	TDS consolidates VIEs in which it has a controlling financial interest as defined by GAAP and is therefore deemed the primary beneficiary. A controlling financial interest will have both of the following characteristics: (a) the power to direct the VIE activities that most significantly impact economic performance; and (b) the obligation to absorb the VIE losses and the right to receive benefits that are significant to the VIE. TDS reviews these criteria initially at the time it enters into agreements and subsequently when events warranting reconsideration occur. These VIEs have risks similar to those described in the “Risk Factors” in TDS’ Form 10-K for the year ended December 31, 2018.

Basis of Presentation (Policies)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The accounting policies of Telephone and Data Systems, Inc. (TDS) conform to accounting principles generally accepted in the United States of America (GAAP) as set forth in the Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC). Unless otherwise specified, references to accounting provisions and GAAP in these notes refer to the requirements of the FASB ASC. The consolidated financial statements include the accounts of TDS and subsidiaries in which it has a controlling financial interest, including TDS’ 82%-owned subsidiary, United States Cellular Corporation (U.S. Cellular) and TDS’ wholly-owned subsidiary, TDS Telecommunications LLC (TDS Telecom). In addition, the consolidated financial statements include certain entities in which TDS has a variable interest that require consolidation under GAAP. All material intercompany accounts and transactions have been eliminated.

TDS’ business segments reflected in this Quarterly Report on Form 10-Q for the period ended September 30, 2019, are U.S. Cellular, Wireline, and Cable. TDS’ non-reportable other business activities are presented as “Corporate, Eliminations and Other”, which includes the operations of TDS’ wholly-owned hosted and managed services (HMS) subsidiary, which operates under the OneNeck IT Solutions brand, and its wholly-owned subsidiary Suttle-Straus, Inc. (Suttle-Straus). HMS’ and Suttle-Straus’ financial results were not significant to TDS’ operations. All of TDS’ segments operate only in the United States. See Note 13 — Business Segment Information for summary financial information on each business segment.

Basis of Accounting

The unaudited consolidated financial statements included herein have been prepared by TDS pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. However, TDS believes that the disclosures included herein are adequate to make the information presented not misleading. Certain numbers included herein are rounded to millions for ease of presentation; however, certain calculated amounts and percentages are determined using the unrounded numbers. These unaudited consolidated financial statements should be read in conjunction with the consolidated financial statements and the notes thereto included in TDS’ Annual Report on Form 10-K (Form 10-K) for the year ended December 31, 2018.

The accompanying unaudited consolidated financial statements contain all adjustments (consisting of normal recurring items, unless otherwise disclosed) necessary for the fair statement of TDS’ financial position as of September 30, 2019 and December 31, 2018, its results of operations, comprehensive income and changes in equity for the three and nine months ended September 30, 2019 and 2018, and its cash flows for the nine months ended September 30, 2019 and 2018. These results are not necessarily indicative of the results to be expected for the full year. TDS has not changed its significant accounting and reporting policies from those disclosed in its Form 10-K for the year ended December 31, 2018, except as disclosed in Note 9 — Leases.

Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Adopted

In June 2016, the FASB issued Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 requires entities to use a new forward-looking, expected loss model to estimate credit losses. It also requires additional disclosure relating to the credit quality of trade and other receivables, including information relating to management’s estimate of credit allowances. TDS is required to adopt ASU 2016-13 on January 1, 2020, using the modified retrospective approach. Early adoption is permitted; however, TDS does not intend to adopt early. The adoption of ASU 2016-13 is not expected to have a significant impact on TDS' financial position or results of operations.

In February 2016, the FASB issued Accounting Standards Update 2016-02, Leases and has since amended the standard with Accounting Standards Update 2018-01, Leases: Land Easement Practical Expedient for Transition to Topic 842, Accounting Standards Update 2018-10, Codification Improvements to Topic 842, Leases, Accounting Standards Update 2018-11, Leases: Targeted Improvements, and Accounting Standards Update 2018-20, Leases: Narrow-Scope Improvements for Lessors, collectively referred to as ASC 842. This standard replaces the previous lease accounting standard under ASC 840 - Leases and requires lessees to record a right-of-use (ROU) asset and lease liability for the majority of leases. TDS adopted the provisions of ASC 842 on January 1, 2019, using a modified retrospective method. Under this method, TDS elected to apply the new accounting standard only to the most recent period presented, recognizing the cumulative effect of the accounting change, if any, as an adjustment to the beginning balance of retained earnings. Accordingly, prior periods have not been recast to reflect the new accounting standard. The cumulative effect of applying the provisions of ASC 842 had no material impact on retained earnings.

Revenue from Contract with Customer

As a practical expedient, costs with an amortization period of one year or less are not capitalized.As a practical expedient, revenue related to contracts of less than one year, generally month-to-month contracts, are excluded from these estimates.

TDS has certain contracts at U.S. Cellular and TDS Telecom in which it bills an amount equal to a fixed per-unit price multiplied by a variable quantity (e.g., certain roaming agreements with other carriers). Because TDS invoices for such items in an amount that corresponds directly with the value of the performance completed to date, TDS may recognize revenue in that amount. As a practical expedient, these contracts are excluded from the estimate of future revenues expected to be recognized related to performance obligations that are unsatisfied as of the end of a reporting period.

Lessee Agreements

A lease is generally present in a contract if the lessee controls the use of identified property, plant or equipment for a period of time in exchange for consideration. Nearly all of TDS’ leases are classified as operating leases, although it does have a small number of finance leases. TDS’ most significant leases are for land and tower spaces, network facilities, retail spaces, and offices.

TDS has agreements with both lease and nonlease components, which are accounted for separately. As part of the present value calculation for the lease liabilities, TDS uses an incremental borrowing rate as the rates implicit in the leases are not readily determinable. The incremental borrowing rates used for lease accounting are based on TDS' unsecured rates, adjusted to approximate the rates at which TDS would be required to borrow on a collateralized basis over a term similar to the recognized lease term. TDS applies the incremental borrowing rates to lease components using a portfolio approach based upon the length of the lease term and the reporting entity in which the lease resides. The cost of nonlease components in TDS’ lease portfolio (e.g., utilities and common area maintenance) are not typically predetermined at lease commencement and are expensed as incurred at their relative standalone price.

Variable lease expense occurs when, subsequent to the lease commencement, lease payments are made that were not originally included in the lease liability calculation. TDS’ variable lease payments are primarily a result of leases with escalations that are tied to an index. The incremental changes due to the index changes are recorded as variable lease expense and are not included in the ROU assets or lease liabilities.

Lease term recognition determines the periods to which expense is allocated and also has a significant impact on the ROU asset and lease liability calculations. Many of TDS’ leases include renewal and early termination options. At lease commencement, the lease terms include options to extend the lease when TDS is reasonably certain that it will exercise the options. The lease terms do not include early termination options unless TDS is reasonably certain to exercise the options. Certain asset classes have similar lease characteristics; therefore, TDS has applied the portfolio approach for lease term recognition for its tower space, retail, and certain ground lease asset classes.

Lessor Agreements

TDS’ most significant lessor leases are for tower space and colocation space. All of TDS’ lessor leases are classified as operating leases. A lease is generally present in a contract if the lessee controls the use of identified property, plant, or equipment for a period of time in exchange for consideration. TDS’ lessor agreements with lease and nonlease components are generally accounted for separately; however, certain service agreements with insignificant lease components are accounted for as nonlease transactions.

Lease term recognition determines the periods to which revenue is allocated over the term of the lease. Many of TDS’ leases include renewal and early termination options. At lease commencement, lease terms include options to extend the lease when TDS is reasonably certain that lessees will exercise the options. Lease terms would not include periods after the date of a termination option that lessees are reasonably certain to exercise.

Variable lease income occurs when, subsequent to the lease commencement, lease payments are received that were not originally included in the lease receivable calculation. TDS’ variable lease income is primarily a result of leases with escalations that are tied to an index. The incremental increases due to the index changes are recorded as variable lease income.

Variable Interest Entities

TDS consolidates VIEs in which it has a controlling financial interest as defined by GAAP and is therefore deemed the primary beneficiary. A controlling financial interest will have both of the following characteristics: (a) the power to direct the VIE activities that most significantly impact economic performance; and (b) the obligation to absorb the VIE losses and the right to receive benefits that are significant to the VIE. TDS reviews these criteria initially at the time it enters into agreements and subsequently when events warranting reconsideration occur. These VIEs have risks similar to those described in the “Risk Factors” in TDS’ Form 10-K for the year ended December 31, 2018.