Commitments and Contingencies (Components Of Lease Expense) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Commitments and Contingencies [Abstract]
Operating lease expense		$ 3,981	$ 4,076	$ 7,693	$ 8,285
Variable lease expense (benefit)	[1]	125	(271)	(25)	(149)
Total lease expense		$ 4,106	$ 3,805	$ 7,668	$ 8,136

[1] Represents amounts incurred in excess of the minimum payments required for the handling and unloading of railcars for a certain lease, offset by railcar lease abatements provided by the lessor when railcars are out of service during periods of maintenance or upgrade.