Fair value measurements - Schedule of Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Financial liabilities
Ceded reinsurance - embedded derivative	$ 34,200	$ 29,700
Fair value
Financial assets
Total financial assets — Asset Management	918,563	908,800
Financial liabilities
Total Liabilities		31,038
Asset Management | Fair value
Financial assets
Equity securities	7,929	10,409
Derivatives	0	13
Other invested assets	71	72
Total financial assets — Asset Management	8,000	10,494
Insurance Solutions
Financial assets
Debt securities:	397,302	405,621
Derivatives	0	481
Financial liabilities
Interest rate swaps	1,792	1,388
Insurance Solutions | Fair value
Financial assets
Equity securities	7,544	15,053
Derivatives	0	481
Corporate loans	140,780	124,067
Total financial assets — Asset Management	780,253	777,145
Financial liabilities
Ceded reinsurance - embedded derivative	34,192	29,650
Interest rate swaps	1,792	1,388
Total Liabilities	35,984	31,038
Insurance Solutions | Variable Interest Entity, Primary Beneficiary | Fair value
Financial assets
Equity securities	1,140	949
Corporate loans	129,170	119,731
Insurance Solutions | Consolidated Balance Including Variable Interest Entity | Fair value
Financial assets
Total financial assets — Asset Management	910,563	897,825
Insurance Solutions | U.S. government and agency
Financial assets
Debt securities:	10,281	10,348
Insurance Solutions | U.S. government and agency | Fair value
Financial assets
Debt securities:	10,281	10,348
Insurance Solutions | U.S. state, territories and municipalities
Financial assets
Debt securities:	3,336	3,440
Insurance Solutions | U.S. state, territories and municipalities | Fair value
Financial assets
Debt securities:	5,230	5,354
Insurance Solutions | Other government and agency | Fair value
Financial assets
Debt securities:	2,444	2,475
Insurance Solutions | Corporate
Financial assets
Debt securities:	158,528	166,693
Insurance Solutions | Corporate | Fair value
Financial assets
Debt securities:	260,389	271,188
Insurance Solutions | Asset and mortgage-backed securities
Financial assets
Debt securities:	222,116	221,524
Insurance Solutions | Asset and mortgage-backed securities | Fair value
Financial assets
Debt securities:	338,135	342,673
Insurance Solutions | Other invested assets
Financial assets
Debt securities:	3,041	3,616
Insurance Solutions | Other invested assets | Fair value
Financial assets
Other invested assets	15,450	5,987
Level 1 | Fair value
Financial assets
Total financial assets — Asset Management	1,431	11,478
Level 1 | Asset Management | Fair value
Financial assets
Equity securities	1,289	3,834
Total financial assets — Asset Management	1,289	3,834
Level 1 | Insurance Solutions | Fair value
Financial assets
Equity securities	142	7,644
Total financial assets — Asset Management	142	7,644
Level 1 | Insurance Solutions | Variable Interest Entity, Primary Beneficiary | Fair value
Financial assets
Corporate loans	0
Level 1 | Insurance Solutions | Consolidated Balance Including Variable Interest Entity | Fair value
Financial assets
Total financial assets — Asset Management	142	7,644
Level 1 | Insurance Solutions | U.S. government and agency | Fair value
Financial assets
Debt securities:	0
Level 2 | Fair value
Financial assets
Total financial assets — Asset Management	591,030	612,830
Financial liabilities
Total Liabilities		31,038
Level 2 | Asset Management | Fair value
Financial assets
Equity securities	0	91
Total financial assets — Asset Management	0	91
Level 2 | Insurance Solutions | Fair value
Financial assets
Equity securities	2,217	2,246
Derivatives	0	481
Corporate loans	18,822	7,499
Total financial assets — Asset Management	591,030	612,258
Financial liabilities
Ceded reinsurance - embedded derivative	34,192	29,650
Interest rate swaps	1,792	1,388
Total Liabilities	35,984	31,038
Level 2 | Insurance Solutions | Variable Interest Entity, Primary Beneficiary | Fair value
Financial assets
Corporate loans	0
Level 2 | Insurance Solutions | Consolidated Balance Including Variable Interest Entity | Fair value
Financial assets
Total financial assets — Asset Management	591,030	612,258
Level 2 | Insurance Solutions | U.S. government and agency | Fair value
Financial assets
Debt securities:	10,281	10,348
Level 2 | Insurance Solutions | U.S. state, territories and municipalities | Fair value
Financial assets
Debt securities:	5,230	5,354
Level 2 | Insurance Solutions | Other government and agency | Fair value
Financial assets
Debt securities:	2,444	2,475
Level 2 | Insurance Solutions | Corporate | Fair value
Financial assets
Debt securities:	245,181	261,039
Level 2 | Insurance Solutions | Asset and mortgage-backed securities | Fair value
Financial assets
Debt securities:	296,855	323,246
Level 2 | Insurance Solutions | Other invested assets | Fair value
Financial assets
Other invested assets	10,000	51
Level 3 | Fair value
Financial assets
Total financial assets — Asset Management	323,931	282,270
Financial liabilities
Total Liabilities		0
Level 3 | Asset Management | Fair value
Financial assets
Equity securities	6,640	6,484
Derivatives	0	13
Other invested assets	71	72
Total financial assets — Asset Management	6,711	6,569
Level 3 | Insurance Solutions | Fair value
Financial assets
Equity securities	3,319	3,240
Corporate loans	121,958	116,568
Total financial assets — Asset Management	186,910	155,021
Level 3 | Insurance Solutions | Variable Interest Entity, Primary Beneficiary | Fair value
Financial assets
Equity securities	1,140	949
Corporate loans	129,170	119,731
Level 3 | Insurance Solutions | Consolidated Balance Including Variable Interest Entity | Fair value
Financial assets
Total financial assets — Asset Management	317,220	275,701
Level 3 | Insurance Solutions | U.S. government and agency | Fair value
Financial assets
Debt securities:	0
Level 3 | Insurance Solutions | Corporate | Fair value
Financial assets
Debt securities:	15,208	10,149
Level 3 | Insurance Solutions | Asset and mortgage-backed securities | Fair value
Financial assets
Debt securities:	41,280	19,427
Level 3 | Insurance Solutions | Other invested assets | Fair value
Financial assets
Other invested assets	5,145	5,637
NAV | Fair value
Financial assets
Total financial assets — Asset Management	2,171	2,222
NAV | Insurance Solutions | Fair value
Financial assets
Equity securities	1,866	1,923
Other invested assets		299
Total financial assets — Asset Management	2,171	2,222
NAV | Insurance Solutions | Variable Interest Entity, Primary Beneficiary | Fair value
Financial assets
Corporate loans	0
NAV | Insurance Solutions | Consolidated Balance Including Variable Interest Entity | Fair value
Financial assets
Total financial assets — Asset Management	2,171	$ 2,222
NAV | Insurance Solutions | U.S. government and agency | Fair value
Financial assets
Debt securities:	0
NAV | Insurance Solutions | Other invested assets | Fair value
Financial assets
Other invested assets	$ 305