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Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Cash and cash equivalents 211,513us-gaap_CashAndCashEquivalentsAtCarryingValue 342,065us-gaap_CashAndCashEquivalentsAtCarryingValue $ 378,358us-gaap_CashAndCashEquivalentsAtCarryingValue $ 424,155us-gaap_CashAndCashEquivalentsAtCarryingValue
Short-term investments   50,104us-gaap_HeldToMaturitySecuritiesCurrent    
Fair Value | Level 1        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Cash and cash equivalents 211,513us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		 342,065us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember		    
Fair Value | Level 2 | Retail        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Long-term debt 608,462us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_PublicDebtMember		 309,852us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_PublicDebtMember		    
Fair Value | Level 2 | Institutional        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Long-term debt 513,647us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_NonPublicDebtMember		 507,697us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_NonPublicDebtMember		    
Fair Value | U.S. Treasury Notes | Level 1        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Short-term investments   50,104us-gaap_HeldToMaturitySecuritiesCurrent
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_EstimateOfFairValueFairValueDisclosureMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_USTreasurySecuritiesMember		    
Book Value        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Cash and cash equivalents 211,513us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		 342,065us-gaap_CashAndCashEquivalentsAtCarryingValue
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember		    
Book Value | Retail        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Long-term debt 617,000us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_PublicDebtMember		 342,000us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_PublicDebtMember		    
Book Value | Institutional        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Long-term debt 532,722us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_NonPublicDebtMember		 532,449us-gaap_LongTermDebtNoncurrent
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_LongtermDebtTypeAxis
= usm_NonPublicDebtMember		    
Book Value | U.S. Treasury Notes        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Short-term investments   50,104us-gaap_HeldToMaturitySecuritiesCurrent
/ us-gaap_FairValueByMeasurementBasisAxis
= us-gaap_CarryingReportedAmountFairValueDisclosureMember
/ us-gaap_InvestmentTypeAxis
= us-gaap_USTreasurySecuritiesMember		    
Institutional        
Fair Value, Balance Sheet Grouping, Financial Statement Captions        
Fair value assumption, interest rate 7.25%usm_FairValueAssumptionsInterestRate
/ us-gaap_LongtermDebtTypeAxis
= usm_NonPublicDebtMember		 7.35%usm_FairValueAssumptionsInterestRate
/ us-gaap_LongtermDebtTypeAxis
= usm_NonPublicDebtMember