Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 125,303
Amortized Cost, Due after one year through five years	114,399
Amortized Cost, Due after five years through ten years	64,251
Amortized Cost, Amortized Cost Due after ten years	9,109
Amortized Cost	315,029	$ 502,167
Fair Value, Due in one year or less	126,261
Fair Value, Due after one year through five years	116,086
Fair Value, Due after five years through ten years	64,191
Fair Value, Due after ten years	9,360
Fair Value	317,916	$ 507,279
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,967
Fair Value	$ 2,018