Quarterly report pursuant to Section 13 or 15(d)

Assets and Liabilities Measured at Fair Value (Narrative) (Details)

v3.10.0.1
Assets and Liabilities Measured at Fair Value (Narrative) (Details)
$ / shares in Units, $ in Thousands
 1 Months Ended 9 Months Ended
Jun. 06, 2017
$ / shares
$ / unit
shares
Jun. 30, 2018
USD ($)
shares
Sep. 30, 2018
USD ($)
shares
Sep. 30, 2017
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Indemnification payment | $     $ 132,725 $ 0
Exchangeable Senior Debentures | 1.75% Exchangeable Debentures | Indemnification obligation        
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Indemnity obligation recorded | $     $ 281,300  
Exchangeable Senior Debentures | 1.75% Exchangeable Debentures | Indemnification obligation | LI LLC        
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Interest rate     1.75%  
Exchangeable instrument, shares outstanding | shares     332,241  
Exchangeable Senior Debentures | 1.75% Exchangeable Debentures | Indemnification obligation | LI LLC | Qurate Retail        
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Number of shares repurchased (in shares) | shares   417,759    
Value of shares repurchased | $   $ 457,000    
Indemnification payment | $   $ 133,000    
Exchangeable Senior Debentures | 1.75% Exchangeable Debentures | Indemnification obligation | Qurate and LI LLC        
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Period in which entities will cooperate with and reasonably assist each other regarding the Purchase Offer     6 months  
LendingTree        
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Number of shares purchased (in shares) | shares 450,000      
LendingTree | Variable forward        
Fair Value Measurement Inputs and Valuation Techniques [Line Items]        
Variable forward contract, term 2 years      
Variable forward contract (in shares) | shares 642,850      
Variable forward contract, closing price (in dollars per share) | $ / shares $ 170.70      
Variable forward contract, floor price (in dollars per share) | $ / unit 128.03      
Variable forward contract, cap price (in dollars per share) | $ / unit 211.67