Transactions with Related Parties (Narrative) (Details) - Affiliated Entity - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Poseidon
Related Party Transaction [Line Items]
Due from related parties	$ 1,700		$ 2,400
Related party transaction, revenues	3,147	$ 3,165
Related party transaction, costs and expenses	254	247
Poseidon \| Asset Management Arrangement
Related Party Transaction [Line Items]
Related party transaction, revenues	2,300	2,200
ANSAC
Related Party Transaction [Line Items]
Due from related parties	66,256		$ 68,075
Related party transaction, revenues	73,079	90,679
Related party transaction, costs and expenses	$ 832	$ 1,057

For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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