CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss), net of tax:	Treasury stock, at cost
Beginning balance at Dec. 31, 2022		$ 0.1	$ 502.6	$ 1,512.4	$ (399.4)	$ (517.4)
Increase (Decrease) in Stockholders' Equity
Options exercised and conversion of common and restricted stock units			(1.4)
Share-based compensation expense			1.9
Net income (loss)	$ 6.6			6.6
Dividends, 2024, $0.34 per share; 2023, $0.33 per share				(13.8)
Change in net unrealized investment losses on fixed maturity securities					93.2
Change in net reserve remeasurements attributable to discount rates	(41.2)				(41.2)
Treasury stock acquired - share repurchase authorization						(4.4)
Ending balance at Mar. 31, 2023	1,139.2	0.1	503.1	1,505.2	(347.4)	(521.8)
Beginning balance at Dec. 31, 2023	1,175.3	0.1	510.9	1,502.2	(314.0)	(523.9)
Increase (Decrease) in Stockholders' Equity
Options exercised and conversion of common and restricted stock units			(0.1)
Share-based compensation expense			2.3
Net income (loss)	26.5			26.5
Dividends, 2024, $0.34 per share; 2023, $0.33 per share				(14.3)
Change in net unrealized investment losses on fixed maturity securities					(19.7)
Change in net reserve remeasurements attributable to discount rates	41.4				41.4
Ending balance at Mar. 31, 2024	$ 1,211.4	$ 0.1	$ 513.1	$ 1,514.4	$ (292.3)	$ (523.9)