v3.26.1
Fair value measurements - Schedule of Realized and Unrealized Gains From Investments (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments     $ (1,876) $ (1,996)
Unrealized gain/(loss) on investments     (11,995) 7,316
Asset Management        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments $ 0 $ 22 367 81
Unrealized gain/(loss) on investments (967) 845 (1,690) 1,627
Net realized and change in unrealized gains (losses) from investment activities (967) 867 (1,318) 1,708
Asset Management | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Unrealized gain/(loss) on investments 0 371   1,339
Net realized and change in unrealized gains (losses) from investment activities 0 371   1,339
Asset Management | Debt obligation | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Unrealized gain/(loss) on investments 0 371   1,339
Net realized and change in unrealized gains (losses) from investment activities 0 371   1,339
Asset Management | Corporate loans        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments     0 0
Unrealized gain/(loss) on investments     0 0
Net realized and change in unrealized gains (losses) from investment activities     5 0
Insurance Solutions | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments (5) (1,965) (14) (2,159)
Unrealized gain/(loss) on investments 2,496 5,998 (2,496) 7,754
Net realized and change in unrealized gains (losses) from investment activities 2,491 4,033 (2,510) 5,595
Insurance Solutions | Variable Interest Entity, Primary Beneficiary        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 59 177 (647) 237
Unrealized gain/(loss) on investments (1,269) (464) (4,240) (789)
Net realized and change in unrealized gains (losses) from investment activities (1,210) (287) (4,887) (552)
Insurance Solutions | Variable Interest Entity, Primary Beneficiary | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 59 177 (647) 237
Unrealized gain/(loss) on investments (1,269) (464) (4,240) (789)
Net realized and change in unrealized gains (losses) from investment activities (1,210) (287) (4,887) (552)
Insurance Solutions | Consolidated Balance Including Variable Interest Entity        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments (330) (1,731) (2,243) (2,088)
Unrealized gain/(loss) on investments 1,008 5,542 (10,305) 7,064
Net realized and change in unrealized gains (losses) from investment activities (726) 3,551 (9,417) 4,758
Insurance Solutions | Consolidated Balance Including Variable Interest Entity | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 54 (1,788) (661) (1,922)
Unrealized gain/(loss) on investments 1,227 5,534 (6,736) 6,965
Net realized and change in unrealized gains (losses) from investment activities 1,281 3,746 (7,397) 5,043
Insurance Solutions | U.S. state, territories and municipalities | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Unrealized gain/(loss) on investments (2) 5 (17) 62
Net realized and change in unrealized gains (losses) from investment activities (2) 5 (17) 62
Insurance Solutions | Other government and agency        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 0 0 0 0
Unrealized gain/(loss) on investments 65 (1) 37 (2)
Net realized and change in unrealized gains (losses) from investment activities 65 (1) 37 (2)
Insurance Solutions | Other government and agency | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Unrealized gain/(loss) on investments 65 (1) 37 (2)
Net realized and change in unrealized gains (losses) from investment activities 65 (1) 37 (2)
Insurance Solutions | Corporate        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments (395) (1,057) (363) (1,068)
Unrealized gain/(loss) on investments 1,991 1,049 (413) 2,236
Net realized and change in unrealized gains (losses) from investment activities 1,596 (8) (776) 1,168
Insurance Solutions | Corporate | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments (4) (1,059) (4) (1,109)
Unrealized gain/(loss) on investments 1,991 1,049 (413) 2,235
Net realized and change in unrealized gains (losses) from investment activities 1,987 (10) (417) 1,126
Insurance Solutions | Asset and mortgage-backed securities        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 1 (94) (209) (252)
Unrealized gain/(loss) on investments 1,042 (299) (1,137) (184)
Net realized and change in unrealized gains (losses) from investment activities 1,043 (393) (1,346) (436)
Insurance Solutions | Asset and mortgage-backed securities | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments (6) (149) (15) (295)
Unrealized gain/(loss) on investments 1,042 (299) (1,137) (184)
Net realized and change in unrealized gains (losses) from investment activities 1,036 (448) (1,152) (479)
Insurance Solutions | Corporate loans        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 5 (2) 5 0
Unrealized gain/(loss) on investments (598) 637 (998) 1,426
Net realized and change in unrealized gains (losses) from investment activities (593) 635 (993) 1,426
Insurance Solutions | Corporate loans | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments 5 (2) 5 0
Unrealized gain/(loss) on investments (598) 637 (998) 1,426
Net realized and change in unrealized gains (losses) from investment activities (593) 635 (993) 1,426
Insurance Solutions | Other invested assets | Fair value option        
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]        
Realized gain/(loss) on investments   (755)   (755)
Unrealized gain/(loss) on investments (2) 4,607 32 4,217
Net realized and change in unrealized gains (losses) from investment activities $ (2) $ 3,852 $ 32 $ 3,462