Investments (Schedule of Amortized Cost and Estimated Fair Value of Debt Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Due in one year or less	$ 119,771
Amortized Cost, Due after one year through five years	284,992
Amortized Cost, Due after five years through ten years	105,656
Amortized Cost, Amortized Cost Due after ten years	25,857
Debt Maturities, Amortized Cost	550,268	$ 604,999
Fair Value, Due in one year or less	120,127
Fair Value, Due after one year through five years	284,947
Fair Value, Due after five years through ten years	102,047
Fair Value, Due after ten years	25,192
Debt securities	545,870	605,746
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Maturities, Amortized Cost	13,992
Debt securities	13,557	16,533
Parent Company [Member]
Schedule of Available-for-sale Securities [Line Items]
Debt Maturities, Amortized Cost	150	150
Debt securities	$ 786	$ 150