Earnings Per Share, Share Repurchases and Dividends on Common Stock (Details 2) - $ / shares shares in Millions	1 Months Ended				12 Months Ended
	May 30, 2017	May 31, 2016	May 31, 2015	May 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic and Diluted [Abstract]
Dilutive effect of stock options and other stock awards granted					1.2	1.6	2.2
Increase (Decrease) in Stock Dividend, Percentage	11.00%	13.00%	14.00%
Common stock dividend (in dollars per share)	$ 1.00	$ 0.90	$ 0.80	$ 0.70	$ 3.90	$ 3.50	$ 3.10