Earnings Per Share, Share Repurchases and Dividends on Common Stock (Unaudited) Earnings Per Share and Dividends (Details 1) - $ / shares shares in Millions	1 Months Ended			3 Months Ended		6 Months Ended
	May 31, 2020	May 31, 2019	May 31, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Basic and Diluted [Abstract]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements				0.4	0.6	0.6	0.6
Common stock dividends per share, declared (in dollars per share)	$ 1.45	$ 1.32	$ 1.20	$ 1.45	$ 1.32	$ 2.77	$ 2.52
Increase in quarterly common stock dividend (percent)	10.00%	10.00%