Financial Instruments (Tables)	9 Months Ended
Sep. 30, 2021
Financial Instruments [Abstract]
Carrying Value, Fair Value And Hierarchy Of Financial Instruments	The following shows the carrying value, fair value and the hierarchy for our financial instruments as of September 30, 2021 (in thousands): Fair Value Measure Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3)Mutual fund investments of deferred compensation plans held in trust$ 102,045 $ 102,045 $ - $ - The following shows the carrying value, fair value and the hierarchy for our financial instruments as of December 31, 2020 (in thousands): Fair Value Measure Carrying Value Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3)Mutual fund investments of deferred compensation plans held in trust$ 86,865 $ 86,865 $ - $ -

Tabular disclosure of the fair value of financial instruments, including financial assets and financial liabilities, and the measurements of those instruments, assets, and liabilities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13467-108611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

Name:	us-gaap_FairValueByBalanceSheetGroupingTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration