Investments - Cost or Amortized Cost and Fair Value of Securities Available for Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 851,826	$ 828,336
Allowance for Expected Credit Losses	(791)
Gross Unrealized Gains	24,532	27,973
Gross Unrealized Losses	(8,318)	(1,025)
Fair Value	867,249	855,284
U.S. Government Obligations and Agencies [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	59,090	53,688
Allowance for Expected Credit Losses	0
Gross Unrealized Gains	2,997	864
Gross Unrealized Losses	(3)	(188)
Fair Value	62,084	54,364
Corporate Bonds [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	464,387	457,180
Allowance for Expected Credit Losses	(665)
Gross Unrealized Gains	11,412	19,179
Gross Unrealized Losses	(6,409)	(141)
Fair Value	468,725	476,218
Mortgage-Backed and Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	314,936	304,285
Fair Value	323,382	311,079
Mortgage-Backed and Asset-Backed Securities [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	314,936	304,285
Allowance for Expected Credit Losses	0
Gross Unrealized Gains	9,839	7,400
Gross Unrealized Losses	(1,393)	(606)
Fair Value	323,382	311,079
Municipal Bonds [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,395	3,397
Allowance for Expected Credit Losses	0
Gross Unrealized Gains	194	103
Gross Unrealized Losses	(3)	(4)
Fair Value	3,586	3,496
Redeemable Preferred Stock [Member] \| Fixed Maturities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,018	9,786
Allowance for Expected Credit Losses	(126)
Gross Unrealized Gains	90	427
Gross Unrealized Losses	(510)	(86)
Fair Value	$ 9,472	$ 10,127

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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