Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 107,108
Amortized Cost, Due after one year through five years	342,962
Amortized Cost, Due after five years through ten years	87,669
Amortized Cost, Amortized Cost Due after ten years	23,760
Debt Maturities, Amortized Cost	569,498	$ 550,268
Fair Value, Due in one year or less	107,605
Fair Value, Due after one year through five years	345,860
Fair Value, Due after five years through ten years	88,061
Fair Value, Due after ten years	24,926
Fair Value	574,279	$ 545,870
Mortgage Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Maturities, Amortized Cost	7,999
Fair Value	$ 7,827