Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 113,961
Amortized Cost, Due after one year through five years	248,003
Amortized Cost, Due after five years through ten years	32,766
Amortized Cost, Amortized Cost Due after ten years	13,467
Debt Maturities, Amortized Cost	414,197	$ 569,498
Fair Value, Due in one year or less	115,144
Fair Value, Due after one year through five years	250,693
Fair Value, Due after five years through ten years	31,560
Fair Value, Due after ten years	14,055
Fair Value	417,569	$ 574,279
Mortgage Backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Maturities, Amortized Cost	6,000
Fair Value	$ 6,117