Summary of significant accounting policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 segment	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Number of business segment									1
Revenue from External Customer [Line Items]
Product sales	$ 5,174	$ 4,848	$ 4,949	$ 4,356	$ 4,799	$ 4,647	$ 4,595	$ 4,151	$ 19,327	$ 18,192	$ 16,639
Restricted investments	0				3,412				0	3,412
NEUPOGEN [Member]
Revenue from External Customer [Line Items]
Product sales									1,159	1,398	1,260
NEUPOGEN [Member] | U.S. federal government stockpiles [Member]
Revenue from External Customer [Line Items]
Product sales										$ 155