Transactions with Related Parties (Narrative) (Details) - Affiliated Entity - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Poseidon
Related Party Transaction [Line Items]
Due from related parties	$ 1,900		$ 1,900		$ 2,400
Related party transaction, revenues	3,102	$ 3,019	9,284	$ 9,420
Related party transaction, costs and expenses	231	240	734	742
Poseidon \| Asset Management Arrangement
Related Party Transaction [Line Items]
Related party transaction, revenues	2,300	2,200	6,800	6,700
ANSAC
Related Party Transaction [Line Items]
Due from related parties	26,106		26,106		$ 68,075
Related party transaction, revenues	44,095	99,878	165,869	272,341
Related party transaction, costs and expenses	$ 528	$ 1,020	$ 1,989	$ 3,356

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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