Basis of Presentation (Policies)	6 Months Ended
Jun. 30, 2020
Accounting Policy Disclosures [Line Items]
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 requires consolidation under GAAP. Intercompany accounts and transactions have been eliminated. TDS’ business segments reflected in this Quarterly Report on Form 10-Q for the period ended June 30, 2020, 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 12 — 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, 2019. 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 June 30, 2020 and December 31, 2019 and its results of operations, comprehensive income and changes in equity for the three and six months ended June 30, 2020 and 2019, and its cash flows for the six months ended June 30, 2020 and 2019. 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, 2019 except as noted below for the estimation of credit losses.
Allowance for Doubtful Accounts	TDS estimates expected credit losses related to accounts receivable balances based on a review of available and relevant information including current economic conditions, projected economic conditions, historical loss experience, account aging, and other factors that could affect collectability. Expected credit losses are determined for each pool of accounts receivable balances that share similar risk characteristics. The allowance for doubtful accounts is the best estimate of the amount of expected credit losses related to existing accounts receivable. TDS does not have any off-balance sheet credit exposure related to its customers.
Recently Adopted Accounting Pronouncements	In June 2016, the FASB issued Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments and subsequently amended the standard with additional Accounting Standards Updates, collectively referred to as ASC 326. This standard requires entities to use a new forward-looking, expected loss model to estimate credit losses and requires additional disclosures relating to the credit quality of trade and other receivables. TDS adopted the provisions of ASC 326 on January 1, 2020, using a modified retrospective method. Under this method, TDS applied 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 326 had no material impact on retained earnings. In August 2018, the FASB issued Accounting Standards Update 2018-15, Intangibles - Goodwill and Other - Internal-Use Software: Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the existing guidance for capitalizing implementation costs for an arrangement that has a software license. The service element of a hosting arrangement will continue to be expensed as incurred. Any capitalized implementation costs will be amortized over the period of the service contract. TDS' hosting arrangements that are service contracts consist primarily of software used to perform administrative functions. TDS adopted ASU 2018-15 on January 1, 2020, using the prospective method. The adoption of ASU 2018-15 did not have a significant impact on TDS' financial position or results of operations.
Revenue from Contract with Customer	As practical expedients, revenue related to contracts of less than one year, generally month-to-month contracts, and contracts with a fixed per-unit price and variable quantity, are excluded from these estimates.TDS expects that commission fees paid as a result of obtaining contracts are recoverable and, therefore, TDS defers and amortizes these costs. As a practical expedient, costs with an amortization period of one year or less are expensed as incurred. TDS also incurs fulfillment costs, such as installation costs, where there is an expectation that a future benefit will be realized. Deferred commission fees and fulfillment costs are amortized based on the timing of transfer of the goods or services to which the assets relate, typically the contract term.
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. TDS reviews the criteria for a controlling financial interest 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 this Form 10-Q and TDS’ Form 10-K for the year ended December 31, 2019.
U.S. Cellular
Accounting Policy Disclosures [Line Items]
Accounts Receivable	U.S. Cellular’s accounts receivable consist primarily of amounts owed by customers for wireless services and equipment sales, including sales of certain devices and accessories under installment plans, by agents and third-party distributors for sales of equipment to them, by third party vendors and by other wireless carriers whose customers have used U.S. Cellular’s wireless systems.
TDS Telecom Total
Accounting Policy Disclosures [Line Items]
Accounts Receivable	TDS Telecom’s accounts receivable primarily consist of amounts owed by customers for services and products provided, by state and federal governments for grants and support funds, and by interexchange carriers for long-distance and data traffic, which TDS Telecom carries on its network.

Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2020

Accounting Policy Disclosures [Line Items]

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 requires consolidation under GAAP. Intercompany accounts and transactions have been eliminated.

TDS’ business segments reflected in this Quarterly Report on Form 10-Q for the period ended June 30, 2020, 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 12 — 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, 2019.

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 June 30, 2020 and December 31, 2019 and its results of operations, comprehensive income and changes in equity for the three and six months ended June 30, 2020 and 2019, and its cash flows for the six months ended June 30, 2020 and 2019. 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, 2019 except as noted below for the estimation of credit losses.

Allowance for Doubtful Accounts

TDS estimates expected credit losses related to accounts receivable balances based on a review of available and relevant information including current economic conditions, projected economic conditions, historical loss experience, account aging, and other factors that could affect collectability. Expected credit losses are determined for each pool of accounts receivable balances that share similar risk characteristics. The allowance for doubtful accounts is the best estimate of the amount of expected credit losses related to existing accounts receivable. TDS does not have any off-balance sheet credit exposure related to its customers.

Recently Adopted Accounting Pronouncements

In June 2016, the FASB issued Accounting Standards Update 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments and subsequently amended the standard with additional Accounting Standards Updates, collectively referred to as ASC 326. This standard requires entities to use a new forward-looking, expected loss model to estimate credit losses and requires additional disclosures relating to the credit quality of trade and other receivables. TDS adopted the provisions of ASC 326 on January 1, 2020, using a modified retrospective method. Under this method, TDS applied 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 326 had no material impact on retained earnings.

In August 2018, the FASB issued Accounting Standards Update 2018-15, Intangibles - Goodwill and Other - Internal-Use Software: Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15). ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the existing guidance for capitalizing implementation costs for an arrangement that has a software license. The service element of a hosting arrangement will continue to be expensed as incurred. Any capitalized implementation costs will be amortized over the period of the service contract. TDS' hosting arrangements that are service contracts consist primarily of software used to perform administrative functions. TDS adopted ASU 2018-15 on January 1, 2020, using the prospective method. The adoption of ASU 2018-15 did not have a significant impact on TDS' financial position or results of operations.

Revenue from Contract with Customer

As practical expedients, revenue related to contracts of less than one year, generally month-to-month contracts, and contracts with a fixed per-unit price and variable quantity, are excluded from these estimates.TDS expects that commission fees paid as a result of obtaining contracts are recoverable and, therefore, TDS defers and amortizes these costs. As a practical expedient, costs with an amortization period of one year or less are expensed as incurred. TDS also incurs fulfillment costs, such as installation costs, where there is an expectation that a future benefit will be realized. Deferred commission fees and fulfillment costs are amortized based on the timing of transfer of the goods or services to which the assets relate, typically the contract term.

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. TDS reviews the criteria for a controlling financial interest 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 this Form 10-Q and TDS’ Form 10-K for the year ended December 31, 2019.

U.S. Cellular

Accounting Policy Disclosures [Line Items]

Accounts Receivable

U.S. Cellular’s accounts receivable consist primarily of amounts owed by customers for wireless services and equipment sales, including sales of certain devices and accessories under installment plans, by agents and third-party distributors for sales of equipment to them, by third party vendors and by other wireless carriers whose customers have used U.S. Cellular’s wireless systems.

TDS Telecom Total

Accounting Policy Disclosures [Line Items]

Accounts Receivable

TDS Telecom’s accounts receivable primarily consist of amounts owed by customers for services and products provided, by state and federal governments for grants and support funds, and by interexchange carriers for long-distance and data traffic, which TDS Telecom carries on its network.