Investments, Summary of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale Debt Securities [Abstract]
Fair value	$ 746,856	$ 795,538
Cost or amortized cost	757,451	783,047
Gross unrealized gains	19,451	16,043
Gross unrealized losses	(30,046)	(3,552)
Net unrealized gains (losses)	(10,595)	12,491
Agency Collateralized Mortgage Obligations [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	10,460	12,093
Cost or amortized cost	11,016	11,557
Gross unrealized gains	390	536
Gross unrealized losses	(946)	0
Net unrealized gains (losses)	(556)	536
Agency Mortgage-backed Securities [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	58,619	56,280
Cost or amortized cost	55,675	54,286
Gross unrealized gains	2,950	2,005
Gross unrealized losses	(6)	(11)
Net unrealized gains (losses)	2,944	1,994
Asset-backed Securities [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	93,369	106,397
Cost or amortized cost	107,774	107,028
Gross unrealized gains	237	499
Gross unrealized losses	(14,642)	(1,130)
Net unrealized gains (losses)	(14,405)	(631)
Bank Loans [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	10,187	14,568
Cost or amortized cost	12,455	14,932
Gross unrealized gains	0	106
Gross unrealized losses	(2,268)	(470)
Net unrealized gains (losses)	(2,268)	(364)
Certificates of Deposit [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	2,835	2,835
Cost or amortized cost	2,835	2,835
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Net unrealized gains (losses)	0	0
Collateralized Mortgage Obligations [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	4,076	5,616
Cost or amortized cost	4,327	5,123
Gross unrealized gains	19	493
Gross unrealized losses	(270)	0
Net unrealized gains (losses)	(251)	493
Corporate Securities [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	262,160	281,381
Cost or amortized cost	263,356	274,340
Gross unrealized gains	4,682	7,492
Gross unrealized losses	(5,878)	(451)
Net unrealized gains (losses)	(1,196)	7,041
Mortgage-backed Securities [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	47,993	47,463
Cost or amortized cost	53,697	46,685
Gross unrealized gains	74	1,047
Gross unrealized losses	(5,778)	(269)
Net unrealized gains (losses)	(5,704)	778
Municipal Obligations [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	39,132	36,286
Cost or amortized cost	38,474	35,749
Gross unrealized gains	916	684
Gross unrealized losses	(258)	(147)
Net unrealized gains (losses)	658	537
Non-U.S. Government Obligations [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	28,842	24,179
Cost or amortized cost	27,992	23,889
Gross unrealized gains	850	290
Gross unrealized losses	0	0
Net unrealized gains (losses)	850	290
U.S. Government Obligations [Member]
Available-for-sale Debt Securities [Abstract]
Fair value	189,183	208,440
Cost or amortized cost	179,850	206,623
Gross unrealized gains	9,333	2,891
Gross unrealized losses	0	(1,074)
Net unrealized gains (losses)	$ 9,333	$ 1,817

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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