Fair Value Measurements (Financial Assets And Liabilities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Investments in marketable securities	$ 20,084	$ 96,765
Total assets	20,084
Liabilities:
Derivatives	30,826
Level 1
Assets:
Investments in marketable securities	6,042
Derivatives	0
Total assets	6,042
Liabilities:
Derivatives	6,336
Level 2
Assets:
Investments in marketable securities	14,042
Total assets	14,042
Liabilities:
Derivatives	24,490
Level 3
Assets:
Investments in marketable securities	0
Derivatives	0
Total assets	0
Liabilities:
Derivatives	$ 0