Debt and lines of credit (Tables)

12 Months Ended

Dec. 31, 2012

Long-term Debt, Unclassified [Abstract]

Schedule of Long-term Debt Instruments

Total long-term debt outstanding as of December 31, 2012 and 2011 is as follows:

	December 31,
	2012			2011
Notes due 2012 at 6.15% (assumed with National acquisition)	$	—		$	375
Floating-rate notes due 2013 (swapped to a 0.922% fixed rate)	1,000			1,000
Notes due 2013 at 0.875%	500			500
Notes due 2014 at 1.375%	1,000			1,000
Notes due 2015 at 3.95% (assumed with National acquisition)	250			250
Notes due 2015 at 0.45%	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 2019 at 1.65%	750			—
	5,625			4,500
Add net unamortized premium	61			93
Less current portion of long-term debt	(1,500		)	(382		)
Total long-term debt	$	4,186		$	4,211