Transactions with Related Parties (Narrative) (Details) - Affiliated Entity - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Poseidon
Related Party Transaction [Line Items]
Related party transaction, revenues	$ 3,242	$ 3,035	$ 7,028	$ 6,182
Due from related parties	2,900		2,900		$ 2,600
Related party transaction, costs and expenses	238	249	478	503
Poseidon \| Asset Management Arrangement
Related Party Transaction [Line Items]
Related party transaction, revenues	2,400	2,300	4,700	4,600
ANSAC
Related Party Transaction [Line Items]
Related party transaction, revenues	71,329	48,695	139,284	121,774
Due from related parties	66,178		66,178		$ 43,400
Related party transaction, costs and expenses	$ 519	$ 629	$ 697	$ 1,461

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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+ Details

- Definition

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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+ Details