Earnings Per Common Share (Calculations) (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Diluted [Abstract]
Weighted average common shares outstanding	236,600,000	236,900,000	236,600,000	236,800,000
Effect of dilutive securities:
Stock options	300,000	700,000	400,000	700,000
Other stock compensation plans	700,000	700,000	600,000	600,000
Potentially dilutive common shares	1,000,000.0	1,400,000	1,000,000.0	1,300,000
Adjusted weighted average common shares outstanding	237,600,000	238,300,000	237,600,000	238,100,000
Dividends per common share (in dollars per share)	$ 0.0051	$ 0.0048	$ 0.0102	$ 0.0096
Outstanding stock options excluded from the computation of diluted earnings per share due to their antidilutive effect	2,700,000		2,100,000	1,000,000.0