CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Millions	Total	Total Equity	Total	Common Shares and Paid-in Surplus	Retained Earnings	AOCL, After-tax	Nonredeemable Noncontrolling Interests
Beginning balance at Dec. 31, 2022		$ 3,935.0	$ 3,746.9	$ 538.6	$ 3,211.8	$ (3.5)	$ 188.1
Increase (Decrease) in Shareholders' Equity
Net income (loss)	$ 509.2	580.9	509.2		509.2		71.7
Other comprehensive income (loss), net of tax		2.4	1.9			1.9	0.5
Total comprehensive income (loss)	511.6	583.3	511.1		509.2	1.9	72.2
Dividends declared on common shares		(2.6)	(2.6)		(2.6)
Dividends to noncontrolling interests		(8.9)					(8.9)
Issuances of common shares		2.1	2.1	2.1
Repurchases and retirements of common shares	(32.7)	(32.7)	(32.7)	(5.1)	(27.6)
BAM member surplus contributions, net of tax		72.8					72.8
Amortization of restricted share awards		15.3	15.3	15.3
Recognition of equity-based compensation expense of subsidiaries		2.4	1.7	1.7			0.7
Net contributions (distributions) and dilution from other noncontrolling interests		4.3	(1.3)	(1.3)			5.6
Disposition of noncontrolling interest		9.4					9.4
Ending balance at Dec. 31, 2023		4,561.6	4,240.5	551.3	3,690.8	(1.6)	321.1
Increase (Decrease) in Shareholders' Equity
Net income (loss)	230.4	284.1	230.4		230.4		53.7
Other comprehensive income (loss), net of tax		(0.1)	(0.1)			(0.1)
Total comprehensive income (loss)	230.3	284.0	230.3		230.4	(0.1)	53.7
Dividends declared on common shares		(2.5)	(2.5)		(2.5)
Dividends to noncontrolling interests		(16.2)					(16.2)
Issuances of common shares		2.9	2.9	2.9
Repurchases and retirements of common shares	(7.9)	(7.9)	(7.9)	(1.1)	(6.8)
BAM member surplus contributions, net of tax		26.0					26.0
Amortization of restricted share awards		16.3	16.3	16.3
Recognition of equity-based compensation expense of subsidiaries		4.4	3.2	3.2			1.2
Net contributions (distributions) and dilution from other noncontrolling interests		(2.2)	0.9	(6.2)	7.1		(3.1)
Impact to noncontrolling interests for the deconsolidation of BAM		153.5					153.5
Acquisition of noncontrolling interests		111.1					111.1
Ending balance at Dec. 31, 2024	5,131.0	5,131.0	4,483.7	566.4	3,919.0	(1.7)	647.3
Temporary equity, ending balance at Dec. 31, 2024	0.0
Increase (Decrease) in Shareholders' Equity
Net income (loss)	1,106.4	1,206.6	1,106.4		1,106.4		100.2
Other comprehensive income (loss), net of tax		3.7	2.5			2.5	1.2
Total comprehensive income (loss)	1,110.1	1,210.3	1,108.9		1,106.4	2.5	101.4
Dividends declared on common shares		(2.6)	(2.6)		(2.6)
Dividends to noncontrolling interests		(26.0)					(26.0)
Issuances of common shares		2.6	2.6	2.6
Repurchases and retirements of common shares	(202.5)	(202.6)	(202.6)	(22.2)	(180.4)
Amortization of restricted share awards		18.5	18.5	18.5
Recognition of equity-based compensation expense of subsidiaries		26.8	16.9	16.9			9.9
Net contributions (distributions) and dilution from other noncontrolling interests		(35.9)	2.8	(3.2)	6.0		(38.7)
Adjustments to redeemable noncontrolling interests		(2.8)	(2.8)		(2.8)
Disposition of noncontrolling interest		99.8					99.8
Acquisition of noncontrolling interests		104.1					104.1
Ending balance at Dec. 31, 2025	6,123.6	$ 6,123.6	$ 5,425.4	$ 579.0	$ 4,845.6	$ 0.8	$ 698.2
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss)	(4.8)
Total comprehensive income (loss)	(4.8)
Adjustments to redeemable noncontrolling interests	2.8
Acquisition of noncontrolling interests	133.5
Temporary equity, ending balance at Dec. 31, 2025	$ 131.5