CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Total Equity	Total	Common shares and paid-in surplus	Retained earnings	AOCI, after tax	Nonredeemable noncontrolling interest
Beginning balances 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)	$ 360.8	408.5	360.8		360.8		47.7
Other comprehensive income (loss), net of tax		1.1	0.6			0.6	0.5
Comprehensive income (loss)	361.9	409.6	361.4		360.8	0.6	48.2
Dividends declared on common shares		(2.5)	(2.5)		(2.5)
Dividends to noncontrolling interests		(9.3)					(9.3)
Issuances of common shares		2.9	2.9	2.9
Repurchases and retirements of common shares		(8.1)	(8.1)	(1.1)	(7.0)
BAM member surplus contribution, net of tax		26.0					26.0
Amortization of restricted share awards		11.8	11.8	11.8
Recognition of equity-based compensation expense of subsidiaries		3.1	2.3	2.3			0.8
Impact to noncontrolling interests for the deconsolidation of BAM		153.5					153.5
Net contributions (distributions) and dilution from other noncontrolling interests		0.1	2.3	(3.9)	6.2		(2.2)
Acquisition of noncontrolling interests — Bamboo		111.1					111.1
Ending balances at Sep. 30, 2024		5,259.8	4,610.6	563.3	4,048.3	(1.0)	649.2
Beginning balances at Jun. 30, 2024		4,872.2	4,422.6	561.3	3,863.1	(1.8)	449.6
Increase (Decrease) in Shareholders' Equity
Net income (loss)	179.0	227.9	179.0		179.0		48.9
Other comprehensive income (loss), net of tax		1.3	0.8			0.8	0.5
Comprehensive income (loss)	180.3	229.2	179.8		179.0	0.8	49.4
Amortization of restricted share awards		4.3	4.3	4.3
Recognition of equity-based compensation expense of subsidiaries		1.0	0.8	0.8			0.2
Impact to noncontrolling interests for the deconsolidation of BAM		153.5					153.5
Net contributions (distributions) and dilution from other noncontrolling interests		(0.4)	3.1	(3.1)	6.2		(3.5)
Ending balances at Sep. 30, 2024		5,259.8	4,610.6	563.3	4,048.3	(1.0)	649.2
Beginning balances at Dec. 31, 2024	5,131.0	5,131.0	4,483.7	566.4	3,919.0	(1.7)	647.3
Increase (Decrease) in Shareholders' Equity
Net income (loss)	270.6	388.9	270.6		270.6		118.3
Other comprehensive income (loss), net of tax		2.5	1.7			1.7	0.8
Comprehensive income (loss)	273.1	391.4	272.3		270.6	1.7	119.1
Dividends declared on common shares		(2.6)	(2.6)		(2.6)
Dividends to noncontrolling interests		(21.2)					(21.2)
Issuances of common shares		2.6	2.6	2.6
Repurchases and retirements of common shares		(9.9)	(9.9)	(1.1)	(8.8)
Amortization of restricted share awards		13.6	13.6	13.6
Recognition of equity-based compensation expense of subsidiaries		9.9	6.5	6.5			3.4
Net contributions (distributions) and dilution from other noncontrolling interests		(35.6)	1.4	(3.4)	4.8		(37.0)
Acquisition of noncontrolling interests — Bamboo		105.5					105.5
Ending balances at Sep. 30, 2025	5,584.7	5,584.7	4,767.6	584.6	4,183.0	0.0	817.1
Temporary equity, beginning balance at Dec. 31, 2024	0.0
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss)	(0.8)
Other comprehensive income (loss), net of tax	(0.8)
Acquisition of noncontrolling interests	133.2
Temporary equity, ending balance at Sep. 30, 2025	132.4
Beginning balances at Jun. 30, 2025		5,340.2	4,644.5	576.6	4,067.6	0.3	695.7
Increase (Decrease) in Shareholders' Equity
Net income (loss)	113.8	162.5	113.8		113.8		48.7
Other comprehensive income (loss), net of tax		(0.6)	(0.3)			(0.3)	(0.3)
Comprehensive income (loss)	113.2	161.9	113.5		113.8	(0.3)	48.4
Dividends to noncontrolling interests		(2.1)					(2.1)
Amortization of restricted share awards		4.9	4.9	4.9
Recognition of equity-based compensation expense of subsidiaries		5.3	3.2	3.2			2.1
Net contributions (distributions) and dilution from other noncontrolling interests		(0.3)	1.5	(0.1)	1.6		(1.8)
Acquisition of noncontrolling interests — Bamboo		74.8					74.8
Ending balances at Sep. 30, 2025	5,584.7	$ 5,584.7	$ 4,767.6	$ 584.6	$ 4,183.0	$ 0.0	$ 817.1
Temporary equity, beginning balance at Jun. 30, 2025	0.0
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss)	(0.8)
Other comprehensive income (loss), net of tax	(0.8)
Acquisition of noncontrolling interests	133.2
Temporary equity, ending balance at Sep. 30, 2025	$ 132.4