Fair value measurements - Investments in Company-Sponsored Funds (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Summary of Investment Holdings [Line Items]
Fair Value	$ 5,373	$ 5,518
Unfunded Commitments	1,314	2,367
Hedge Funds
Summary of Investment Holdings [Line Items]
Fair Value	283	446
Unfunded Commitments	$ 0	$ 0
Hedge Funds | Minimum
Summary of Investment Holdings [Line Items]
Redemption notice period	30 days	30 days
Hedge Funds | Maximum
Summary of Investment Holdings [Line Items]
Redemption notice period	120 days	120 days
Private Equity Funds
Summary of Investment Holdings [Line Items]
Fair Value	$ 5,090	$ 5,072
Unfunded Commitments	$ 1,314	$ 2,367