Other Current Assets (Narrative) (Details) - USD ($)	3 Months Ended	6 Months Ended
Mar. 31, 2020	Jun. 30, 2020	Jun. 30, 2019
Other current assets
Proceeds on disposition of assets	$ 15,555,000	$ 16,106,000	$ 583,000
Gain on sale of assets	$ 1,090,000

Amount of gain (loss) on sale or disposal of assets, including but not limited to property plant and equipment, intangible assets and equity in securities of subsidiaries or equity method investee.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Name:	us-gaap_GainLossOnDispositionOfAssets1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration