Earnings Per Common Share (Calculations) (Details) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Diluted [Abstract]
Weighted average common shares outstanding	237,100,000	242,200,000	236,900,000	245,800,000
Effect of dilutive securities:
Stock options	700,000	700,000	600,000	800,000
Other stock compensation plans	700,000	700,000	700,000	700,000
Potentially dilutive common shares	1,400,000	1,400,000	1,300,000	1,500,000
Adjusted weighted average common shares outstanding	238,500,000	243,600,000	238,200,000	247,300,000
Dividends per common share (in dollars per share)	$ 0.0051	$ 0.0048	$ 0.0147	$ 0.0138
Outstanding stock options excluded from the computation of diluted earnings per share due to their antidilutive effect	1,000,000	1,000,000.0	1,000,000.0