Earnings Per Share, Share Repurchases and Dividends on Common Stock (Unaudited) (Details 2) - $ / shares shares in Millions	1 Months Ended		3 Months Ended
	May 31, 2016	May 31, 2015	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share, Basic and Diluted [Abstract]
Dilutive effect of of stock awards and options granted to employees under stock-based compensation plans			1.3	2.1
Common stock dividends per share, declared (in dollars per share)	$ 0.90	$ 0.80	$ 0.90	$ 0.80
Increase in quarterly common stock dividend (percent)	13.00%