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Investments Investment Balances (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Investments [Abstract]    
Joint ventures $ 604,964 $ 534,430
Nonmarketable securities 14,171 11,746
Marketable equity securities 37,109 33,637
Total $ 656,244 $ 579,813