Shareholders' Equity (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended	156 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount	$ 115,018			$ 115,018
Common stock surrendered as payment	102,956	$ 198,563	$ 166,147	$ 2,800,000
Repurchases in Accordance with Stock Award Agreements [Member]
Equity, Class of Treasury Stock [Line Items]
Common stock surrendered as payment	$ 48,555	$ 10,420	$ 5,411

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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