v3.26.1
Fair Value Measurement (Schedule of Fair Value of Assets) (Details) - USD ($)
$ in Thousands
Mar. 31, 2026
Dec. 31, 2025
Assets:    
Fixed maturities, available-for-sale $ 3,643,213 $ 3,685,787
Fixed maturities, trading 13,567 14,316
Equity investments 105,708 106,988
U.S. Treasury obligations    
Assets:    
Fixed maturities, available-for-sale 182,402 219,402
U.S. Government-sponsored enterprise obligations    
Assets:    
Fixed maturities, available-for-sale 8,846 9,852
State and municipal bonds    
Assets:    
Fixed maturities, available-for-sale 437,732 430,063
Residential mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 592,619 591,841
Agency commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 5,205 5,360
Other commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 217,245 208,121
Other asset-backed securities    
Assets:    
Fixed maturities, available-for-sale 455,842 459,634
Level 3 | Corporate debt, limited observable inputs    
Assets:    
Fixed maturities, available-for-sale 83,883 79,511
Recurring    
Assets:    
Total assets categorized within the fair value hierarchy 4,288,186 4,309,179
Recurring | Fair Value, Inputs, Level 1, 2 and 3    
Assets:    
Fixed maturities, trading 13,567 14,316
Other assets 1,765 789
Total assets categorized within the fair value hierarchy 4,073,763 4,094,724
Liabilities:    
Other liabilities 2,410 1,284
Total liabilities categorized within the fair value hierarchy 2,410 1,284
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | U.S. Treasury obligations    
Assets:    
Fixed maturities, available-for-sale 182,402 219,402
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | U.S. Government-sponsored enterprise obligations    
Assets:    
Fixed maturities, available-for-sale 8,846 9,852
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | State and municipal bonds    
Assets:    
Fixed maturities, available-for-sale 437,732 430,063
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Corporate debt, multiple observable inputs    
Assets:    
Fixed maturities, available-for-sale 1,659,439 1,682,003
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Corporate debt, limited observable inputs    
Assets:    
Fixed maturities, available-for-sale 83,883 79,511
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Residential mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 592,619 591,841
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Agency commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 5,205 5,360
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Other commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 217,245 208,121
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Other asset-backed securities    
Assets:    
Fixed maturities, available-for-sale 455,842 459,634
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Financial    
Assets:    
Equity investments 12,759 13,206
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Utilities/Energy    
Assets:    
Equity investments 1,525 1,103
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Bond funds    
Assets:    
Equity investments 80,695 81,137
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | All other    
Assets:    
Equity investments 10,729 11,542
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Short-term investments    
Assets:    
Short-term and other investments 309,510 285,629
Recurring | Fair Value, Inputs, Level 1, 2 and 3 | Other investments    
Assets:    
Short-term and other investments   1,215
Recurring | Level 1    
Assets:    
Fixed maturities, trading 0 0
Other assets 0 390
Total assets categorized within the fair value hierarchy 343,747 327,364
Liabilities:    
Other liabilities 2,124 809
Total liabilities categorized within the fair value hierarchy 2,124 809
Recurring | Level 1 | U.S. Treasury obligations    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | U.S. Government-sponsored enterprise obligations    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | State and municipal bonds    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Corporate debt, multiple observable inputs    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Corporate debt, limited observable inputs    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Residential mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Agency commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Other commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Other asset-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 1 | Financial    
Assets:    
Equity investments 10,391 10,838
Recurring | Level 1 | Utilities/Energy    
Assets:    
Equity investments 1,525 1,103
Recurring | Level 1 | Bond funds    
Assets:    
Equity investments 80,695 81,137
Recurring | Level 1 | All other    
Assets:    
Equity investments 10,729 11,542
Recurring | Level 1 | Short-term investments    
Assets:    
Short-term and other investments 240,407 222,354
Recurring | Level 1 | Other investments    
Assets:    
Short-term and other investments   0
Recurring | Level 2    
Assets:    
Fixed maturities, trading 13,567 14,316
Other assets 1,765 399
Total assets categorized within the fair value hierarchy 3,640,787 3,684,345
Liabilities:    
Other liabilities 286 475
Total liabilities categorized within the fair value hierarchy 286 475
Recurring | Level 2 | U.S. Treasury obligations    
Assets:    
Fixed maturities, available-for-sale 182,402 219,402
Recurring | Level 2 | U.S. Government-sponsored enterprise obligations    
Assets:    
Fixed maturities, available-for-sale 8,846 9,852
Recurring | Level 2 | State and municipal bonds    
Assets:    
Fixed maturities, available-for-sale 437,732 430,063
Recurring | Level 2 | Corporate debt, multiple observable inputs    
Assets:    
Fixed maturities, available-for-sale 1,659,439 1,682,003
Recurring | Level 2 | Corporate debt, limited observable inputs    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 2 | Residential mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 592,619 591,841
Recurring | Level 2 | Agency commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 5,205 5,360
Recurring | Level 2 | Other commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 217,245 208,121
Recurring | Level 2 | Other asset-backed securities    
Assets:    
Fixed maturities, available-for-sale 450,496 456,130
Recurring | Level 2 | Financial    
Assets:    
Equity investments 2,368 2,368
Recurring | Level 2 | Utilities/Energy    
Assets:    
Equity investments 0 0
Recurring | Level 2 | Bond funds    
Assets:    
Equity investments 0 0
Recurring | Level 2 | All other    
Assets:    
Equity investments 0 0
Recurring | Level 2 | Short-term investments    
Assets:    
Short-term and other investments 69,103 63,275
Recurring | Level 2 | Other investments    
Assets:    
Short-term and other investments   1,215
Recurring | Level 3    
Assets:    
Fixed maturities, trading 0 0
Other assets 0 0
Total assets categorized within the fair value hierarchy 89,229 83,015
Liabilities:    
Other liabilities 0 0
Total liabilities categorized within the fair value hierarchy 0 0
Recurring | Level 3 | U.S. Treasury obligations    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | U.S. Government-sponsored enterprise obligations    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | State and municipal bonds    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | Corporate debt, multiple observable inputs    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | Corporate debt, limited observable inputs    
Assets:    
Fixed maturities, available-for-sale 83,883 79,511
Recurring | Level 3 | Residential mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | Agency commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | Other commercial mortgage-backed securities    
Assets:    
Fixed maturities, available-for-sale 0 0
Recurring | Level 3 | Other asset-backed securities    
Assets:    
Fixed maturities, available-for-sale 5,346 3,504
Recurring | Level 3 | Financial    
Assets:    
Equity investments 0 0
Recurring | Level 3 | Utilities/Energy    
Assets:    
Equity investments 0 0
Recurring | Level 3 | Bond funds    
Assets:    
Equity investments 0 0
Recurring | Level 3 | All other    
Assets:    
Equity investments 0 0
Recurring | Level 3 | Short-term investments    
Assets:    
Short-term and other investments 0 0
Recurring | Level 3 | Other investments    
Assets:    
Short-term and other investments   0
Recurring | Fair Value Measured at Net Asset Value Per Share | Equity investments    
Assets:    
Total assets categorized within the fair value hierarchy $ 214,423 $ 214,455