Quarterly report pursuant to Section 13 or 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 ($)
shares in Thousands, $ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]          
Carrying amount $ 174,134   $ 174,134   $ 114,655
Share of earnings (losses) $ 10,856 $ 1,648 $ 18,714 $ 4,971  
LendingTree          
Schedule of Equity Method Investments [Line Items]          
Percentage ownership 25.05%   25.05%    
Market value $ 792,462   $ 792,462    
Carrying amount 171,027   171,027   114,655
Share of earnings (losses) $ 10,200 $ 1,700 15,500 $ 5,000  
Additional shares acquired 220        
Other          
Schedule of Equity Method Investments [Line Items]          
Carrying amount $ 3,107   $ 3,107   $ 0