Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 28.8	$ 41.8	$ 120.0	$ 66.6
Other comprehensive income (loss):
Foreign currency translation adjustments	(0.3)	(2.9)	(0.1)	(4.0)
Unrealized gains (losses) on securities:
Gains (losses) arising during the year	41.9	(36.7)	98.7	(61.4)
Reclassification adjustment for losses included in net income	1.8	15.1	4.9	2.6
Other comprehensive income (loss) before tax	43.4	(24.5)	103.5	(62.8)
Income tax provision related to other comprehensive income (loss):
Gains (losses) arising during the year	6.7	(5.3)	15.8	(9.3)
Reclassification adjustment for losses included in net income	0.2	2.5	0.7	0.2
Income tax provision (benefit) related to other comprehensive income (loss)	6.9	(2.8)	16.5	(9.1)
Other comprehensive income (loss), net of tax	36.5	(21.7)	87.0	(53.7)
Comprehensive income	$ 65.3	$ 20.1	$ 207.0	$ 12.9

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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