Earnings Per Share, Share Repurchases and Dividends on Common Stock (Unaudited) (Details 2) - $ / shares shares in Millions	1 Months Ended			3 Months Ended		6 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share, Basic and Diluted [Abstract]
Dilutive effect of of stock awards and options granted to employees under stock-based compensation plans				1.0	1.4	1.1	1.7
Common stock dividends per share, declared (in dollars per share)	$ 1.00	$ 0.90	$ 0.80			$ 1.90	$ 1.70
Increase in quarterly common stock dividend (percent)	11.00%	13.00%