Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Millions	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)
Balance at beginning of period at Dec. 31, 2023		$ 5.7	$ 41.0	$ 3,356.9	$ (54.8)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised			15.8
Stock-based compensation			2.0
Net income	$ 297.7			297.7
Cash dividends paid				(223.2)
Other comprehensive income (loss)					(11.9)
Balance at end of period at Mar. 31, 2024	$ 3,429.2	5.7	58.8	3,431.4	(66.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends paid per share of common stock (in dollars per share)	$ 0.39
Balance at beginning of period at Dec. 31, 2023		5.7	41.0	3,356.9	(54.8)
Balance at end of period at Dec. 31, 2024	$ 3,616.3	5.7	88.6	3,613.5	(91.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends paid per share of common stock (in dollars per share)	$ 1.56
Stock options exercised			11.2
Stock-based compensation			2.0
Net income	$ 298.7			298.7
Cash dividends paid				(246.7)
Other comprehensive income (loss)					8.8
Balance at end of period at Mar. 31, 2025	$ 3,690.3	$ 5.7	$ 101.8	$ 3,665.5	$ (82.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends paid per share of common stock (in dollars per share)	$ 0.43