Acquisition-related charges (Details) (National [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		15 Months Ended	6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		21 Months Ended	3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012 Jobs	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member]	Jun. 30, 2013 Amortization of intangible assets [Member]	Jun. 30, 2012 Amortization of intangible assets [Member]	Jun. 30, 2013 Amortization of intangible assets [Member]	Jun. 30, 2012 Amortization of intangible assets [Member]	Jun. 30, 2013 Retention bonuses [Member]	Jun. 30, 2012 Retention bonuses [Member]	Jun. 30, 2013 Retention bonuses [Member]	Jun. 30, 2012 Retention bonuses [Member]	Jun. 30, 2013 Severance and other benefits [Member]	Jun. 30, 2012 Severance and other benefits [Member]	Jun. 30, 2013 Severance and other benefits [Member]	Jun. 30, 2012 Severance and other benefits [Member]	Jun. 30, 2013 Severance and other benefits [Member]	Jun. 30, 2013 Stock-based compensation [Member]	Jun. 30, 2012 Stock-based compensation [Member]	Jun. 30, 2013 Stock-based compensation [Member]	Jun. 30, 2012 Stock-based compensation [Member]	Jun. 30, 2013 Transaction and other costs [Member]	Jun. 30, 2012 Transaction and other costs [Member]	Jun. 30, 2013 Transaction and other costs [Member]	Jun. 30, 2012 Transaction and other costs [Member]	Jun. 30, 2013 As recorded in Acquisition charges [Member]	Jun. 30, 2012 As recorded in Acquisition charges [Member]	Jun. 30, 2013 As recorded in Acquisition charges [Member]	Jun. 30, 2012 As recorded in Acquisition charges [Member]	Jun. 30, 2013 Distributor contract termination [Member]	Jun. 30, 2012 Distributor contract termination [Member]	Jun. 30, 2013 Distributor contract termination [Member]	Jun. 30, 2012 Distributor contract termination [Member]	Dec. 31, 2012 Distributor contract termination [Member]	Dec. 31, 2011 Distributor contract termination [Member] Distributors
Business Acquisition [Line Items]
Acquisition-related costs	$ 86	$ 104	$ 171	$ 278				$ 81	$ 81	$ 162	$ 162	$ 2	$ 7	$ 3	$ 48	$ 0	$ 3	$ 0	$ 15	$ 86	$ 3	$ 4	$ 6	$ 10	$ 0	$ 9	$ 0	$ 22	$ 86	$ 104	$ 171	$ 257	$ 0	$ 0	$ 0	$ 21	$ 21
Identified intangible assets subject to amortization, Weighted Average Useful Life (Years)						2 years	10 years
Restructuring and Related Cost, Number of Positions Eliminated					350
Business Acquisition, Amount Related to Severance and Other Benefit Costs Paid																				$ 81
Business Acquistion, Number of distributors discontinued																																						1