Investments - Schedule of Investments in Two Sigma Funds (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Marketable Securities [Line Items]
Cost	$ 1,471,985	$ 1,355,563
Net Unrealized Gains (Losses)	401,894	232,095
Investments in Two Sigma Funds, at fair value	1,873,879	1,587,658
Two Sigma Spectrum Portfolio, LLC
Marketable Securities [Line Items]
Cost	48,246	500,616
Net Unrealized Gains (Losses)	19,105	131,996
Investments in Two Sigma Funds, at fair value	67,351	632,612
Two Sigma Equity Spectrum Portfolio, LLC
Marketable Securities [Line Items]
Cost	769,374	187,718
Net Unrealized Gains (Losses)	280,203	49,906
Investments in Two Sigma Funds, at fair value	1,049,577	237,624
Two Sigma Absolute Return Portfolio, LLC
Marketable Securities [Line Items]
Cost	9,789	93,092
Net Unrealized Gains (Losses)	3,210	8,882
Investments in Two Sigma Funds, at fair value	12,999	101,974
Two Sigma Futures Portfolio, LLC
Marketable Securities [Line Items]
Cost	236,926	192,064
Net Unrealized Gains (Losses)	49,433	44,998
Investments in Two Sigma Funds, at fair value	286,359	237,062
Two Sigma Horizon Portfolio, LLC
Marketable Securities [Line Items]
Cost	266,392	241,090
Net Unrealized Gains (Losses)	22,480	4,585
Investments in Two Sigma Funds, at fair value	288,872	245,675
Two Sigma Navigator Portfolio, LLC
Marketable Securities [Line Items]
Cost	125,927	110,577
Net Unrealized Gains (Losses)	27,418	(9,585)
Investments in Two Sigma Funds, at fair value	153,345	100,992
Two Sigma Kuiper Portfolio, LLC
Marketable Securities [Line Items]
Cost	15,331	30,406
Net Unrealized Gains (Losses)	45	1,313
Investments in Two Sigma Funds, at fair value	$ 15,376	$ 31,719