Basis Of Presentation And New Accounting Standards - New Accounting Standards (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Long-term debt	$ 299,560	$ 258,912
Common stock	1,286,380	1,327,592
Retained earnings	468,087	464,524
Deferred tax liabilities	$ 100,655	110,821
Cumulative-effect adjustments upon adoption of ASU | Accounting Standards Update 2020-06
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)