Debt and lines of credit (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Schedule of long-term debt Instruments

Long-term debt outstanding as of December 31, 2014 and 2013 is as follows:

	December 31,
	2014			2013
Notes due 2014 at 1.375%	$	—		$	1,000
Notes due 2015 at 3.95% (assumed with National acquisition)	250			250
Notes due 2015 at 0.45%	750			750
Notes due 2016 at 2.375%	1,000			1,000
Notes due 2017 at 6.60% (assumed with National acquisition)	375			375
Notes due 2017 at 0.875%	250			—
Notes due 2018 at 1.00%	500			500
Notes due 2019 at 1.65%	750			750
Notes due 2021 at 2.75%	250			—
Notes due 2023 at 2.25%	500			500
	4,625			5,125
Net unamortized premium	17			33
Current portion of long-term debt	(1,001		)	(1,000		)
Long-term debt	$	3,641		$	4,158