Investments - Summary of Selected Financial information for Asset Management Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Feb. 28, 2025	Nov. 30, 2024	Sep. 30, 2024	Feb. 29, 2024
Schedule of Equity Method Investments [Line Items]
Total assets		$ 70,218,891	$ 64,360,309
Total liabilities		59,950,046	54,134,916
Total members’ equity		$ 10,268,439	$ 10,224,987		$ 9,867,469
Hildene Insurance Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Net increase in members’ equity resulting from operations	$ 8,400
Hildene Insurance Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Total assets	359,100			$ 304,200
Total liabilities	31,800			200
Total members’ equity	$ 327,300			$ 304,000