Consolidated Statement of Changes in Stockholders' Equity - USD ($) $ in Millions	Total	Cumulative change related to the adoption of ASU 2016-13	Cumulative effect, period of adoption, adjusted balance	Common stock	Common stock Cumulative change related to the adoption of ASU 2016-13	Common stock Cumulative effect, period of adoption, adjusted balance	Retained earnings	Retained earnings Cumulative change related to the adoption of ASU 2016-13	Retained earnings Cumulative effect, period of adoption, adjusted balance	Accumulated other comprehensive loss	Accumulated other comprehensive loss Cumulative change related to the adoption of ASU 2016-13	Accumulated other comprehensive loss Cumulative effect, period of adoption, adjusted balance
Equity, beginning balance at Dec. 31, 2022	$ 3,073.8			$ 2,478.2			$ 1,072.7			$ (477.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	56.3			0.0			56.3			0.0
Other comprehensive income (loss), net of tax expense	$ 78.0			0.0			0.0			78.0
Stock repurchased and retired (in shares)	55,080
Non-vested common shares issued (in shares)	10,863
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	15,788
Common stock transactions:
Common shares purchased and retired	$ (1.8)			(1.8)			0.0			0.0
Non-vested common shares issued	0.0			0.0			0.0			0.0
Non-vested common shares forfeited or canceled	0.0			0.0			0.0			0.0
Stock-based compensation expense	$ 2.3			2.3			0.0			0.0
Common dividends (in dollars per share)	$ 0.47
Common cash dividend declared	$ (48.3)			0.0			(48.3)			0.0
Equity, ending balance at Mar. 31, 2023	3,160.3			2,478.7			1,080.7			(399.1)
Equity, beginning balance at Dec. 31, 2023	3,227.5	$ 1.2	$ 3,228.7	2,448.9	$ 0.0	$ 2,448.9	1,135.1	$ 1.2	$ 1,136.3	(356.5)	$ 0.0	$ (356.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58.4			0.0			58.4			0.0
Other comprehensive income (loss), net of tax expense	$ (30.4)			0.0			0.0			(30.4)
Stock repurchased and retired (in shares)	43,690
Non-vested common shares issued (in shares)	685,363
Stock Issued During Period, Shares, Restricted Stock Award, Forfeited	11,676
Common stock transactions:
Common shares purchased and retired	$ (1.1)			(1.1)			0.0			0.0
Non-vested common shares issued	0.0			0.0			0.0			0.0
Non-vested common shares forfeited or canceled	0.0			0.0			0.0			0.0
Stock-based compensation expense	$ 2.9			2.9			0.0			0.0
Common dividends (in dollars per share)	$ 0.47
Common cash dividend declared	$ (48.8)			0.0			(48.8)			0.0
Equity, ending balance at Mar. 31, 2024	$ 3,209.7			$ 2,450.7			$ 1,145.9			$ (386.9)