Basis of presentation and significant accounting policies and practices (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Percent of revenue from sales to distributors	60.00%
Percent of distributor revenue from sales of consigned inventory	60.00%
Advertising expense	$ 45	$ 46	$ 46
Maximum length to maturity of a security, from the investment date, where it is classified as cash and cash equivalent	90 days
Length to maturity from the investment date of a security where the length of time is too short to be classified as a short-term investment	90 days
Consigned inventory	$ 258	$ 202