Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions		Total	Common Stock [Member]		Additional Paid-In Capital [Member]		Retained Earnings [Member]		Accumulated Other Comprehensive Loss [Member]		Deferred Compensation [Member]		Treasury Stock, Preferred	Treasury Stock, Common
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		108,000
Common Stock, Dividends, Per Share, Declared		$ 1.230
Beginning Balances (shares) at Dec. 31, 2023	[1],[2]		22,235,000
Beginning Balances at Dec. 31, 2023		$ 1,246.1	$ 10.8	[1]	$ 749.4		$ 488.7		$ (2.8)		$ 9.1			$ (9.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		64.4					64.4
Other comprehensive income (loss)		1.2							1.2
Other Comprehensive Income (Loss), Net of Tax		1.2
Dividend declared							(27.6)
Retirement savings plan and dividend reinvestment plan (shares)	[1],[2],[3]		28,000
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan	[3]	3.0	$ 0.1	[1]	2.9
Share-based compensation (shares)	[1],[2],[4],[5]		36,000
Share-based compensation and tax benefit	[4],[5]		$ 0.0	[1]	3.5
Treasury stock activities	[2]										0.6			(0.6)
Ending Balances (shares) at Jun. 30, 2024	[1],[2]		22,299,000
Ending Balances at Jun. 30, 2024		$ 1,290.6	$ 10.9	[1]	755.8		525.5		(1.6)		9.7			(9.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation		14,000
Common Stock, Dividends, Per Share, Declared		$ 0.640
Beginning Balances (shares) at Mar. 31, 2024	[1],[2]		22,267,000
Beginning Balances at Mar. 31, 2024		$ 1,280.9	$ 10.8	[1]	750.2		521.7		(1.8)		9.6		$ (9.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		18.2
Other comprehensive income (loss)		0.2							0.2
Other Comprehensive Income (Loss), Net of Tax		0.2
Dividend declared		(14.4)					(14.4)
Retirement savings plan and dividend reinvestment plan (shares)	[1],[2],[3]		25,000
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan	[3]	2.7	$ 0.1	[1]	2.6
Share-based compensation (shares)	[1],[2],[4],[5]		7,000
Share-based compensation and tax benefit	[4],[5]	3.0	$ 0.0	[1]	3.0
Treasury stock activities							0.0				0.1			(0.1)
Ending Balances (shares) at Jun. 30, 2024	[1],[2]		22,299,000
Ending Balances at Jun. 30, 2024		$ 1,290.6	$ 10.9	[1]	755.8		525.5		(1.6)		9.7			(9.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		113,000
Preferred Stock, Shares Authorized		2,000,000,000
Preferred Stock, Par or Stated Value Per Share		$ 10.00
Shares Held In Trust For Deferred Compensation Plan		114,000
Common Stock, Dividends, Per Share, Declared		$ 1.325
Beginning Balances (shares) at Dec. 31, 2024	[1],[2],[6]		22,899,000
Beginning Balances at Dec. 31, 2024		$ 1,390.2	$ 11.1	[1],[6]	830.5	[6]	550.3	[6]	(1.7)	[6]	9.8	[6]		(9.8)	[6]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		74.8					74.8
Other comprehensive income (loss)		(1.1)							(1.1)
Other Comprehensive Income (Loss), Net of Tax		(1.1)
Dividend declared							(31.0)
Retirement savings plan and dividend reinvestment plan (shares)	[1],[2],[3]		486,000
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan	[3]		$ 0.3	[1]	60.9
Share-based compensation (shares)	[1],[2],[4],[5]		35,000
Share-based compensation and tax benefit	[4],[5]		$ 0.0	[1]	5.0
Treasury stock activities	[2]										2.7			(2.7)
Ending Balances (shares) at Jun. 30, 2025	[1],[2]		23,420,000
Ending Balances at Jun. 30, 2025		$ 1,499.1	$ 11.4	[1]	896.4		594.1		(2.8)		12.5			(12.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation		8,000
Stock Issued, Value, During The Period Shares Retirement Savings Plan And Dividend Reinvestment Plan	[3]	$ 61.2
Common Stock, Dividends, Per Share, Declared		$ 0.685
Beginning Balances (shares) at Mar. 31, 2025	[1],[2]		23,089,000
Beginning Balances at Mar. 31, 2025		$ 1,447.3	$ 11.2	[1]	852.0		586.4		(2.3)		12.2		$ (12.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income		23.9					23.9
Other comprehensive income (loss)		(0.5)							(0.5)
Other Comprehensive Income (Loss), Net of Tax		(0.5)
Dividend declared		(16.2)					(16.2)
Retirement savings plan and dividend reinvestment plan (shares)	[1],[2],[3]		325,000
Stock Issued During The Period Value Retirement Savings Plan And Dividend Reinvestment Plan	[3]	41.4	$ 0.2	[1]	41.2
Share-based compensation (shares)	[1],[2],[4],[5]		6,000
Share-based compensation and tax benefit	[4],[5]	3.2	$ 0.0	[1]	3.2
Treasury stock activities							0.0				0.3			(0.3)
Ending Balances (shares) at Jun. 30, 2025	[1],[2]		23,420,000
Ending Balances at Jun. 30, 2025		$ 1,499.1	$ 11.4	[1]	$ 896.4		$ 594.1		$ (2.8)		$ 12.5			$ (12.5)
Preferred Stock, Shares Authorized		2,000,000
Preferred Stock, Par or Stated Value Per Share		$ 10.00
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares Held In Trust For Deferred Compensation Plan		127,000

[1] 2.0 million shares of preferred stock at $0.01 par value have been authorized. No preferred shares have been issued or are outstanding; accordingly, no information has been included in the Condensed Consolidated Statements of Stockholders’ Equity.    

[2] Includes 127 thousand, 114 thousand, 113 thousand, and 108 thousand shares at June 30, 2025, December 31, 2024, June 30, 2024 and December 31, 2023, respectively, held in a Rabbi Trust related to our Non-Qualified Deferred Compensation Plan.

[3] Includes shares issued under the Retirement Savings Plan, DRIP and/or ATM program, as applicable.

[4] Includes amounts for shares issued for directors’ compensation.

[5] The shares issued under the SICP are net of shares withheld for employee taxes. For the six months ended June 30, 2025 and 2024, we withheld 8 thousand and 14 thousand shares, respectively, for employee taxes.

[6]