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Investments Investment Balances (Details) - USD ($)
$ in Thousands
Dec. 31, 2019
Dec. 31, 2018
Investments [Abstract]    
Joint ventures $ 534,430 $ 486,032
Nonmarketable securities 11,746 9,177
Marketable equity securities 33,637 33,513
Total $ 579,813 $ 528,722