Earnings per share (Tables)

12 Months Ended

Dec. 31, 2015

Earnings Per Share [Abstract]

Earnings per share reconciliation

The following table provides a reconciliation between basic and diluted earnings per share

In millions, except per share data	Year ended December 31,		2015		2014		2013
Net income		$	3,538	$	3,167	$	2,612
Weighted-average basic shares outstanding			800.7		819.9		843.1
Dilutive effect of stock-based compensation			4.4		3.6		3.0
Weighted-average diluted shares outstanding			805.1		823.5		846.1
Basic earnings per share		$	4.42	$	3.86	$	3.10
Diluted earnings per share		$	4.39	$	3.85	$	3.09