Annual report pursuant to Section 13 and 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 12 Months Ended
Jun. 06, 2017
$ / shares
$ / unit
shares
Jun. 30, 2018
USD ($)
shares
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]          
Indemnification payment | $     $ 132,725 $ 0 $ 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      
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