Investments, Available-for-sale Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 714,817	$ 514,237
Gross Unrealized Holding Gains	17,029	2,882
Gross Unrealized Holding Losses	2,314	6,868
Estimated Fair Value	729,532	510,251
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	110	610
Gross Unrealized Holding Gains	2	2
Gross Unrealized Holding Losses	0	1
Estimated Fair Value	112	611
Obligations of States, Municipalities and Political Subdivisions [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	166,312	153,884
Gross Unrealized Holding Gains	7,542	2,010
Gross Unrealized Holding Losses	961	1,294
Estimated Fair Value	172,893	154,600
Corporate and Other Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	180,287	97,889
Gross Unrealized Holding Gains	4,736	264
Gross Unrealized Holding Losses	255	1,401
Estimated Fair Value	184,768	96,752
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	195,750	151,137
Gross Unrealized Holding Gains	2,930	252
Gross Unrealized Holding Losses	710	1,522
Estimated Fair Value	197,970	149,867
Residential Mortgage-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	172,358	110,717
Gross Unrealized Holding Gains	1,819	354
Gross Unrealized Holding Losses	388	2,650
Estimated Fair Value	$ 173,789	$ 108,421

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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