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, 2020		$ 5.7	$ 59.1	$ 2,689.6	$ (21.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised			6.6
Stock-based compensation			1.5
Net earnings	$ 210.6			210.6
Dividends paid in cash				(160.8)
Translation adjustment upon merger of foreign subsidiary				0.0
Other comprehensive income (loss)					(4.4)
Balance at end of period at Mar. 31, 2021	$ 2,786.7	5.7	67.2	2,739.4	(25.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends paid per share of common stock (in dollars per share)	$ 0.28
Balance at beginning of period at Dec. 31, 2020		5.7	59.1	2,689.6	(21.2)
Balance at end of period at Dec. 31, 2021	$ 3,042.2	5.8	96.2	2,970.9	(30.7)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends paid per share of common stock (in dollars per share)	$ 1.12
Stock options exercised			3.9
Stock-based compensation			1.5
Net earnings	$ 269.6			269.6
Dividends paid in cash				(178.4)
Translation adjustment upon merger of foreign subsidiary				0.9
Other comprehensive income (loss)					2.3
Balance at end of period at Mar. 31, 2022	$ 3,142.0	$ 5.8	$ 101.6	$ 3,063.0	$ (28.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividends paid per share of common stock (in dollars per share)	$ 0.31