Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (16.2)	$ 69.8	$ (17.2)	$ 99.6
Foreign currency translation:
Foreign currency translation adjustments	(4.5)	3.4	(0.4)	2.5
Reclassification adjustment for foreign currency translation included in net income	4.5	0.0	31.8	0.0
Defined benefit pension plans:
Net gain arising during the year	0.0	1.9	0.0	1.9
Unrealized losses on fixed maturity securities:
(Losses) gains arising during the year	(150.4)	33.3	(322.4)	(28.8)
Reclassification adjustment for losses (gains) included in net income	0.0	(15.2)	(5.4)	(19.2)
Other comprehensive (loss) income before tax	(150.4)	23.4	(296.4)	(43.6)
Defined benefit pension plans:
Net gain arising during the year	0.0	0.4	0.0	0.4
Unrealized gains (losses) on fixed maturity securities:
(Losses) gains arising during the year	(29.3)	5.5	(62.1)	(6.3)
Reclassification adjustment for (gains) included in net income	0.0	(1.5)	(1.0)	(2.3)
Income tax (benefit) provision related to other comprehensive income (loss)	(29.3)	4.4	(63.1)	(8.2)
Other comprehensive (loss) income, net of tax	(121.1)	19.0	(233.3)	(35.4)
Comprehensive (loss) income	$ (137.3)	$ 88.8	$ (250.5)	$ 64.2