Condensed Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (6.4)	$ 28.8	$ (25.2)	$ 120.0
Other comprehensive income (loss):
Foreign currency translation adjustments	(4.2)	(0.3)	(7.6)	(0.1)
Unrealized gains (losses) on fixed maturity securities:
Gains arising during the year	152.9	41.9	30.1	98.7
Reclassification adjustment for (gains) losses included in net income	(16.5)	1.8	(19.9)	4.9
Other comprehensive income before tax	132.2	43.4	2.6	103.5
Income tax provision related to other comprehensive income:
Gains arising during the year	27.0	6.7	5.9	15.8
Reclassification adjustment for (gains) losses included in net income	(2.6)	0.2	(0.7)	0.7
Income tax provision related to other comprehensive income	24.4	6.9	5.2	16.5
Other comprehensive income (loss), net of tax	107.8	36.5	(2.6)	87.0
Comprehensive income (loss)	$ 101.4	$ 65.3	$ (27.8)	$ 207.0