Annual report pursuant to Section 13 and 15(d)

Investments in Affiliates Accounted for Using the Equity Method (Investment in Lending Tree) (Details)

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Investments in Affiliates Accounted for Using the Equity Method (Investment in Lending Tree) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]      
Carrying amount $ 177,030 $ 114,655  
Share of earnings (losses) of affiliates $ 25,772 7,001 $ 11,831
LendingTree      
Schedule of Equity Method Investments [Line Items]      
Percentage ownership 26.60%    
Market value $ 756,197    
Carrying amount 174,002 114,655  
Share of earnings (losses) of affiliates 21,100 7,000 $ 11,800
Other      
Schedule of Equity Method Investments [Line Items]      
Carrying amount $ 3,028 $ 0