CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($) $ in Millions	Total	Common shares and paid-in surplus	Retained earnings	AOCI, after tax	Total	Non-controlling interest	Total Equity	BAM	BAM Non-controlling interest	Marketing Technology (MediaAlpha)	Marketing Technology (MediaAlpha) Non-controlling interest
Beginning Balances at Dec. 31, 2018	$ 2,718.2	$ 584.0	$ 2,264.9	$ (5.8)	$ 2,843.1	$ (124.9)
Increase (Decrease) in Shareholders' Equity
Net income	331.3		353.6		353.6	(22.3)
Net change in foreign currency translation and other	(5.8)			(5.5)	(5.5)	(0.3)
Total comprehensive income (loss)	347.8		353.6	(5.5)	348.1	(22.6)	$ 325.5
Dividends declared on common shares	(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests	(1.6)					(1.6)
Repurchases and retirements of common shares	(4.9)	(1.1)	(3.8)		(4.9)
Issuances of common shares	2.2	2.2			2.2
Capital contributions from BAM members, net of tax								$ 36.3	$ 36.3
Net contributions and dilution from other non-controlling interests	2.3					2.3
Amortization of restricted share awards	7.8	7.8			7.8
Acquisition of non-controlling interests	1.8					1.8
Effect of deconsolidation of MediaAlpha										$ (13.8)	$ (13.8)
Recognition of equity-based compensation expense of subsidiary	0.3	0.3			0.3
Ending Balances at Sep. 30, 2019	3,070.9	593.2	2,611.5	(11.3)	3,193.4	(122.5)
Beginning Balances at Jun. 30, 2019	3,007.9	590.5	2,562.8	(9.0)	3,144.3	(136.4)
Increase (Decrease) in Shareholders' Equity
Net income	43.2		48.7		48.7	(5.5)
Net change in foreign currency translation and other	(2.4)			(2.3)	(2.3)	(0.1)
Total comprehensive income (loss)	46.3		48.7	(2.3)	46.4	(5.6)	40.8
Dividends to non-controlling interests	(0.6)					(0.6)
Capital contributions from BAM members, net of tax								19.3	19.3
Net contributions and dilution from other non-controlling interests	0.8					0.8
Amortization of restricted share awards	2.7	2.7			2.7
Ending Balances at Sep. 30, 2019	3,070.9	593.2	2,611.5	(11.3)	3,193.4	(122.5)
Beginning Balances at Dec. 31, 2019	3,144.7	596.3	2,672.4	(7.2)	3,261.5	(116.8)
Increase (Decrease) in Shareholders' Equity
Net income	190.0		219.5		219.5	(29.5)
Net change in foreign currency translation and other	1.0			0.7	0.7	0.3
Total comprehensive income (loss)	220.5		219.5	0.7	220.2	(29.2)	191.0
Dividends declared on common shares	(3.2)		(3.2)		(3.2)
Dividends to non-controlling interests	(2.3)					(2.3)
Repurchases and retirements of common shares	(85.2)	(18.6)	(66.6)		(85.2)
Issuances of common shares	1.5	1.5			1.5
Capital contributions from BAM members, net of tax								46.9	46.9
Net contributions and dilution from other non-controlling interests	1.7	(0.4)			(0.4)	2.1
Amortization of restricted share awards	12.3	12.3			12.3
Acquisition of non-controlling interests	0.8					0.8
Recognition of equity-based compensation expense of subsidiary	1.0	1.0			1.0
Ending Balances at Sep. 30, 2020	3,309.2	592.1	2,822.1	(6.5)	3,407.7	(98.5)
Beginning Balances at Jun. 30, 2020	3,063.3	587.0	2,589.3	(10.3)	3,166.0	(102.7)
Increase (Decrease) in Shareholders' Equity
Net income	222.0		232.9		232.9	(10.9)
Net change in foreign currency translation and other	4.0			3.8	3.8	0.2
Total comprehensive income (loss)	236.8		232.9	3.8	236.7	(10.7)	$ 226.0
Dividends to non-controlling interests	(0.9)					(0.9)
Repurchases and retirements of common shares	(0.1)		(0.1)		(0.1)
Issuances of common shares	0.2	0.2			0.2	0.0
Capital contributions from BAM members, net of tax								$ 15.4	$ 15.4
Net contributions and dilution from other non-controlling interests	(0.1)	0.3			0.3	(0.4)
Amortization of restricted share awards	3.6	3.6			3.6
Acquisition of non-controlling interests	0.8					0.8
Recognition of equity-based compensation expense of subsidiary	1.0	1.0			1.0
Ending Balances at Sep. 30, 2020	$ 3,309.2	$ 592.1	$ 2,822.1	$ (6.5)	$ 3,407.7	$ (98.5)