Investments (Fair Value and Losses by Investment Category and Length of Time in a Loss Position) (Details) - Fixed maturities - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	$ 341,897	$ 211,240
Less than Twelve Months, Gross Unrealized Losses	10,361	3,131
Twelve Months or More, Fair Value	235,267	293,974
Twelve Months or More, Gross Unrealized Losses	19,904	20,712
Total, Fair Value	577,164	505,214
Total, Gross Unrealized Losses	30,265	23,843
Foreign government bonds
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	5,853	2,152
Less than Twelve Months, Gross Unrealized Losses	102	1
Twelve Months or More, Fair Value	0	400
Twelve Months or More, Gross Unrealized Losses	0	0
Total, Fair Value	5,853	2,552
Total, Gross Unrealized Losses	102	1
U.S. public corporate securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	123,987	81,622
Less than Twelve Months, Gross Unrealized Losses	4,311	984
Twelve Months or More, Fair Value	2,137	19,206
Twelve Months or More, Gross Unrealized Losses	863	1,263
Total, Fair Value	126,124	100,828
Total, Gross Unrealized Losses	5,174	2,247
U.S. private corporate securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	55,349	33,264
Less than Twelve Months, Gross Unrealized Losses	2,553	780
Twelve Months or More, Fair Value	2,533	22,143
Twelve Months or More, Gross Unrealized Losses	108	226
Total, Fair Value	57,882	55,407
Total, Gross Unrealized Losses	2,661	1,006
Foreign public corporate securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	25,254	3,839
Less than Twelve Months, Gross Unrealized Losses	1,558	23
Twelve Months or More, Fair Value	5,335	9,379
Twelve Months or More, Gross Unrealized Losses	1,920	362
Total, Fair Value	30,589	13,218
Total, Gross Unrealized Losses	3,478	385
Foreign private corporate securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	57,886	32,800
Less than Twelve Months, Gross Unrealized Losses	1,374	921
Twelve Months or More, Fair Value	155,079	186,693
Twelve Months or More, Gross Unrealized Losses	16,351	18,630
Total, Fair Value	212,965	219,493
Total, Gross Unrealized Losses	17,725	19,551
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	56,042	32,361
Less than Twelve Months, Gross Unrealized Losses	416	243
Twelve Months or More, Fair Value	70,183	55,461
Twelve Months or More, Gross Unrealized Losses	662	223
Total, Fair Value	126,225	87,822
Total, Gross Unrealized Losses	1,078	466
Commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	17,526	22,153
Less than Twelve Months, Gross Unrealized Losses	47	163
Twelve Months or More, Fair Value	0	0
Twelve Months or More, Gross Unrealized Losses	0	0
Total, Fair Value	17,526	22,153
Total, Gross Unrealized Losses	47	163
Residential mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than Twelve Months, Fair Value	0	3,049
Less than Twelve Months, Gross Unrealized Losses	0	16
Twelve Months or More, Fair Value	0	692
Twelve Months or More, Gross Unrealized Losses	0	8
Total, Fair Value	0	3,741
Total, Gross Unrealized Losses	$ 0	$ 24