Basis Of Presentation And New Accounting Standards - New Accounting Standards (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	$ 261,668	$ 258,912
Common stock	1,290,697	1,327,592
Retained earnings	437,065	464,524
Deferred tax liabilities	$ 91,785	110,821
Cumulative Effect, Period of Adoption | Accounting Standards Update 2020-06 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt		44,100
Common stock		(41,500)
Retained earnings		6,700
Deferred tax liabilities		$ (9,300)