Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 150,383
Amortized Cost, Due after one year through five years	140,739
Amortized Cost, Due after five years through ten years	32,369
Amortized Cost, Amortized Cost Due after ten years	17,359
Amortized Cost	344,232	$ 502,167
Fair Value, Due in one year or less	151,762
Fair Value, Due after one year through five years	143,504
Fair Value, Due after five years through ten years	32,165
Fair Value, Due after ten years	17,704
Fair Value	348,525	$ 507,279
Mortgage Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,382
Fair Value	$ 3,390