Earnings Per Common Share (Calculations) (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Diluted [Abstract]
Weighted average common shares outstanding	236,900,000	244,900,000	236,800,000	247,400,000
Effect of dilutive securities:
Stock options	700,000	800,000	700,000	800,000
Other stock compensation plans	700,000	700,000	600,000	700,000
Potentially dilutive common shares	1,400,000	1,500,000	1,300,000	1,500,000
Adjusted weighted average common shares outstanding	238,300,000	246,400,000	238,100,000	248,900,000
Dividends per common share (in dollars per share)	$ 0.0048	$ 0.0045	$ 0.0096	$ 0.0090
Outstanding stock options excluded from the computation of diluted earnings per share due to their antidilutive effect	1,000,000	1,100,000.0	1,000,000.0	1,100,000