Summary of significant accounting policies (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended					12 Months Ended							3 Months Ended					12 Months Ended
	Mar. 31, 2013 2013 Results of Adjustments	Dec. 31, 2012 2013 Results of Adjustments	Sep. 30, 2012 2013 Results of Adjustments	Jun. 30, 2012 2013 Results of Adjustments	Mar. 31, 2012 2013 Results of Adjustments	Dec. 31, 2013 2013 Results of Adjustments	Dec. 31, 2012 2013 Results of Adjustments	Dec. 31, 2011 2013 Results of Adjustments	Dec. 31, 2010 2013 Results of Adjustments	Dec. 31, 2013 2013 Results of Adjustments Online subscriptions	Dec. 31, 2013 2013 Results of Adjustments Europe	Dec. 31, 2013 2013 Results of Adjustments Blizzard	Mar. 31, 2012 2012 Results of Adjustments	Dec. 31, 2011 2012 Results of Adjustments	Sep. 30, 2011 2012 Results of Adjustments	Jun. 30, 2011 2012 Results of Adjustments	Mar. 31, 2011 2012 Results of Adjustments	Dec. 31, 2012 2012 Results of Adjustments	Dec. 31, 2011 2012 Results of Adjustments	Dec. 31, 2010 2012 Results of Adjustments	Dec. 31, 2009 2012 Results of Adjustments	Dec. 31, 2012 2012 Results of Adjustments Online subscriptions	Dec. 31, 2012 2012 Results of Adjustments Europe	Dec. 31, 2012 2012 Results of Adjustments Blizzard
Results of Adjustments [Line Items]
Correction of Error - Net Revenues						$ 8				$ 8	$ 8	$ 8						$ 11				$ 11	$ 11	$ 11
Correction of Error - Interest and Other Investment Income (Expense)						1
Correction of Error - Income Before Income Tax Expense						9				9	9	9										11	11	11
Correction of Error - Net Income	1	1	1	1	1	7	4	2	1				1	1	1	1	1	8	3	2	3
Correction of Error - Accrued Expenses and Other Liabilities						9
Correction of Error - Deferred Revenues																		11
Correction of Error - Operating Cash Flows						$ (9)
Correction of Error - Basic and Diluted EPS						$ (0.01)												$ (0.01)