Earnings Per Share, Share Repurchases and Dividends on Common Stock (Details 1) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended				21 Months Ended	44 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Sep. 16, 2015	Dec. 04, 2014	May 15, 2013
Stock Repurchase [Line Items]
Shares Repurchased	1.6	7.3		19.3
May 2013 Share Repurchase Program Original Authorization
Stock Repurchase [Line Items]
Amount Authorized									$ 4,000
Total Shares Retired						32.8
Average Price Per Share						$ 121.97
Shares Repurchased	0.0	0.0		2.7
December 2014 Share Repurchase Original Authorization
Stock Repurchase [Line Items]
Amount Authorized								$ 3,000
Total Shares Retired			18.0
Average Price Per Share			$ 166.70
Shares Repurchased	0.0	1.4		16.6
September 2015 Share Repurchase Original Authorization
Stock Repurchase [Line Items]
Amount Authorized							$ 4,000
Total Shares Retired					7.4
Average Price Per Share					$ 222.93
Shares Repurchased	1.6	5.9		0.0
Amount repurchased					$ 1,700
Amount remaining under authorization for share repurchases	$ 2,300				$ 2,300