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Stock-Based Compensation Plans - Nonqualified Stock Options, Assumptions and Other Disclosures (Details) - Nonqualified Stock Options - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock-Based Compensation Plans - Disclosures
Options granted (in shares)	0.8
Assumptions used to estimate fair value of stock options granted during period
Weighted-average expected volatility (as a percent)	34.20%	25.70%	23.30%
Weighted-average expected term	7 years	7 years	7 years
Weighted-average risk-free interest rate (as a percent)	1.20%	1.30%	2.60%
Weighted-average expected dividend yield (as a percent)	3.82%	4.33%	4.07%
Weighted-average estimated fair value of stock options granted (in dollars per share)	$ 15.67	$ 9.64	$ 10.00
Other nonqualified stock option disclosures
Unrecognized compensation costs	$ 3.0
Weighted-average service period over which unrecognized compensation costs will be recognized	1 year 9 months 18 days
Cash received from stock options exercised	$ 42.2	$ 4.4	$ 3.4
Tax benefits realized for the tax deductions from options exercised	$ 9.1	$ 1.4	$ 0.5

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