CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Shares and Paid-in Surplus	Retained Earnings	AOCL, After-tax	Total	Non-controlling Interests	Total Equity
Beginning balance at Dec. 31, 2017		$ 670.6	$ 2,823.2	$ (1.3)	$ 3,492.5	$ (131.7)	$ 3,360.8
Increase (Decrease) in Shareholders' Equity
Net income (loss)	$ (191.4)		(141.2)		(141.2)	(50.2)	(191.4)
Net change in foreign currency translation and interest rate swap				(4.5)	(4.5)	(0.3)	(4.8)
Comprehensive income (loss)			(141.2)	(4.5)	(145.7)	(50.5)	(196.2)
Dividends declared on common shares			(3.8)		(3.8)		(3.8)
Dividends to non-controlling interests						(8.0)	(8.0)
Issuances of common shares		2.0			2.0		2.0
Repurchases and retirements of common shares	(519.1)	(105.8)	(413.3)		(519.1)	0.0	(519.1)
Capital contributions from BAM members, net of tax						45.0	45.0
Amortization of restricted share awards		13.0			13.0	0.0	13.0
Recognition of compensation costs for equity-based units of subsidiary		7.4			7.4	4.3	11.7
Dilution from equity units of subsidiary		(1.5)			(1.5)	1.5	0.0
Acquisition of non-controlling interests						14.5	14.5
Acquisition of subsidiary		(1.7)			(1.7)		(1.7)
Ending balance at Dec. 31, 2018		584.0	2,264.9	(5.8)	2,843.1	(124.9)	2,718.2
Increase (Decrease) in Shareholders' Equity
Net income (loss)	376.6		414.5		414.5	(37.9)	376.6
Net change in foreign currency translation and interest rate swap				(1.4)	(1.4)	0.0	(1.4)
Comprehensive income (loss)			414.5	(1.4)	413.1	(37.9)	375.2
Dividends declared on common shares			(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests						(2.0)	(2.0)
Issuances of common shares		2.2			2.2		2.2
Repurchases and retirements of common shares	(4.9)	(1.1)	(3.8)		(4.9)		(4.9)
Capital contributions from BAM members, net of tax						57.6	57.6
Amortization of restricted share awards		10.6			10.6		10.6
Recognition of compensation costs for equity-based units of subsidiary		1.5			1.5		1.5
Net contributions from other non-controlling interests		(0.9)			(0.9)	2.4	1.5
Acquisition of non-controlling interests						1.8	1.8
Deconsolidation of non-controlling interests associated with the MediaAlpha Transaction						(13.8)	(13.8)
Ending balance at Dec. 31, 2019	3,144.7	596.3	2,672.4	(7.2)	3,261.5	(116.8)	3,144.7
Increase (Decrease) in Shareholders' Equity
Net income (loss)	663.4		708.7		708.7	(45.3)	663.4
Net change in foreign currency translation and interest rate swap				6.8	6.8	0.5	7.3
Comprehensive income (loss)			708.7	6.8	715.5	(44.8)	670.7
Dividends declared on common shares			(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests						(2.1)	(2.1)
Issuances of common shares		1.5			1.5		1.5
Repurchases and retirements of common shares	(85.1)	(18.5)	(66.7)		(85.2)		(85.2)
Capital contributions from BAM members, net of tax						68.9	68.9
Amortization of restricted share awards		16.6			16.6		16.6
Recognition of compensation costs for equity-based units of subsidiary		2.3			2.3	0.1	2.4
Net contributions from other non-controlling interests		(3.0)			(3.0)	5.3	2.3
Acquisition of non-controlling interests						1.3	1.3
Ending balance at Dec. 31, 2020	$ 3,817.9	$ 595.2	$ 3,311.2	$ (0.4)	$ 3,906.0	$ (88.1)	$ 3,817.9