Summary of significant accounting policies (Policies)	9 Months Ended
Sep. 30, 2011
Summary of significant accounting policies
Revenue Recognition	Revenue Recognition Revenue Arrangements with Multiple Deliverables On January 1, 2011, we adopted amendments to an accounting standard related to revenue recognition for arrangements with multiple deliverables (which standard, as amended, is referred to herein as the “new accounting principles”). The new accounting principles establish a selling price hierarchy for determining the selling price of a deliverable and require the application of the relative selling price method to allocate the arrangement consideration to each deliverable in a multiple deliverables revenue arrangement. Certain of our revenue arrangements have multiple deliverables and, as such, are accounted for under the new accounting principles. These revenue arrangements include product sales consisting of both software and hardware deliverables (such as peripherals or other ancillary collectors' items sold together with physical “boxed” software) and our sales of World of Warcraft boxed products, expansion packs and value-added services, each of which is considered with the related subscription services for these purposes. Our assessment of deliverables and units of accounting does not change under the new accounting principles. Pursuant to the guidance of ASU 2009-13, when a revenue arrangement contains multiple elements, such as hardware and software products, licenses and/or services, we allocate revenue to each element based on a selling price hierarchy. The selling price for a deliverable is based on its vendor-specific-objective-evidence (“VSOE”) if it is available, third-party evidence (“TPE”) if VSOE is not available, or best estimated selling price (“BESP”) if neither VSOE nor TPE is available. In multiple element arrangements where more-than-incidental software deliverables are included, revenue is allocated to each separate unit of accounting for each of the non-software deliverables and to the software deliverables as a group using the relative selling prices of each of the deliverables in the arrangement based on the aforementioned selling price hierarchy. If the arrangement contains more than one software deliverable, the arrangement consideration allocated to the software deliverables as a group is then allocated to each software deliverable using the guidance for recognizing software revenue. As noted above, when neither VSOE nor TPE is available for a deliverable, we use BESP. We do not have significant revenue arrangements that require BESP for the three or nine months ended September 30, 2011. The inputs we use to determine the selling price of our significant deliverables include the actual price charged by the Company for a deliverable that the Company sells separately, which represents the VSOE, and the wholesale prices of the same or similar products, which represents TPE. The pattern and timing of revenue recognition for deliverables and allocation of the arrangement consideration did not change upon the adoption of the new accounting principles. Also, we do not expect the adoption of the new accounting principles to have a material effect on our financial statements in the periods after our initial adoption. Product Sales We recognize revenue from the sale of our products upon the transfer of title and risk of loss to our customers and once any performance obligations have been completed. Certain products are sold to customers with a street date (i.e., the earliest date these products may be sold by retailers). For these products, we recognize revenue on the later of the street date and the sale date. Revenue from product sales is recognized after deducting the estimated allowance for returns and price protection. For our software products with online functionality, we evaluate whether those features or functionality are more than an inconsequential separate deliverable in addition to the software product. This evaluation is performed for each software product and any online transaction, such as a digital download of a title or product add-ons, when it is released. When we determine that a software title contains online functionality that constitutes a more-than-inconsequential separate service deliverable in addition to the product, principally because of its importance to gameplay, we consider our performance obligations for this title to extend beyond the sale of the game. VSOE of fair value does not exist for the online functionality, as we do not separately charge for this component of the title. As a result, we recognize all of the software-related revenue from the sale of the title ratably over the estimated service period, which is estimated to begin the month after the later of the sale date and the street date of the title. In addition, we initially defer the costs of sales for the title (excluding intangible asset amortization), and recognize the costs of sales as the related revenues are recognized. Cost of sales includes manufacturing costs, software royalties and amortization, and intellectual property licenses costs. We recognize revenues from World of Warcraft boxed product, expansion packs and value-added services, in each case with the related subscription service revenue, ratably over the estimated service periods beginning upon activation of the software and delivery of the related services. Revenues attributed to the sale of World of Warcraft boxed software and related expansion packs are classified as product sales and revenues attributable to subscriptions and other value-added services are classified as subscription, licensing and other revenues. Revenues for software products with more-than-inconsequential separate service deliverables and World of Warcraft products are recognized over the estimated service periods, which range from a minimum of five months to a maximum of less than a year. For our software products with features we consider to be incidental to the overall product offering and an inconsequential deliverable, such as products which provide limited online features at no additional cost to the consumer, we recognize the related revenue from them upon the transfer of title and risk of loss of the product to our customer. With respect to online transactions, such as online downloads of titles or product add-ons that do not include a more-than-inconsequential separate service deliverable, revenue is recognized when the fee is paid by the online customer to purchase online content, the product is available for download and is activated for gameplay. In addition, persuasive evidence of an arrangement must exist and collection of the related receivable must be probable. Sales incentives and other consideration given by us to our customers, such as rebates and product replacement fees, are considered adjustments of the selling price of our products and are reflected as reductions to revenue. Sales incentives and other consideration that represent costs incurred by us for assets or services received, such as the appearance of our products in a customer's national circular ad, are reflected as sales and marketing expenses when the benefit from the sales incentive is separable from sales to the same customer and we can reasonably estimate the fair value of the benefit. Subscription Revenues Subscription revenues are derived from World of Warcraft, a game that is playable through Blizzard's servers on a subscription-only basis. After the first month of free usage that is included with the World of Warcraft boxed software, the World of Warcraft end user may enter into a subscription agreement for additional future access. Revenues associated with the sale of subscriptions via boxed software and prepaid subscription cards, as well as prepaid subscriptions sales, are deferred until the subscription service is activated by the consumer and recognized ratably over the subscription period. Revenue from internet gaming rooms in Asia is recognized upon usage of the time packages sold. Value-added service revenues associated with subscriptions are recognized ratably over the estimated service periods. Licensing Revenues Third-party licensees in Russia, China and Taiwan distribute and host Blizzard's World of Warcraft game in their respective countries under license agreements with Blizzard. We receive royalties from the licensees as a result. We recognize these royalties as revenues based on the end users' activation of the underlying prepaid time, if all other performance obligations have been completed, or based on usage by the end user when we have continuing service obligations. We recognize any upfront licensing fee received over the term of the contracts. With respect to license agreements that provide customers the right to make multiple copies in exchange for guaranteed amounts, revenue is generally recognized upon delivery of a master copy. Per copy royalties on sales that exceed the guarantee are recognized as earned. In addition, persuasive evidence of an arrangement must exist and collection of the related receivable must be probable. Breakage Revenues World of Warcraft boxed product sales and subscription revenues are recognized upon activation of the game. We analyze historical activation patterns over time to determine when the likelihood of activation ever occurring becomes remote. We recognize revenues from subscriptions that have not yet been activated, prepaid subscription cards, as well as prepaid subscription sales, when the likelihood of future activation occurring is remote (defined as “breakage revenues”). Other Revenues Other revenues primarily include licensing activity of intellectual property other than software to third-parties. Revenue is recorded upon receipt of licensee statements, or upon the receipt of cash, provided the license period has begun.

Summary of significant accounting policies (Policies)

9 Months Ended

Sep. 30, 2011

Summary of significant accounting policies

Revenue Arrangements with Multiple Deliverables

On January 1, 2011, we adopted amendments to an accounting standard related to revenue recognition for arrangements with multiple deliverables (which standard, as amended, is referred to herein as the “new accounting principles”). The new accounting principles establish a selling price hierarchy for determining the selling price of a deliverable and require the application of the relative selling price method to allocate the arrangement consideration to each deliverable in a multiple deliverables revenue arrangement. Certain of our revenue arrangements have multiple deliverables and, as such, are accounted for under the new accounting principles. These revenue arrangements include product sales consisting of both software and hardware deliverables (such as peripherals or other ancillary collectors' items sold together with physical “boxed” software) and our sales of World of Warcraft boxed products, expansion packs and value-added services, each of which is considered with the related subscription services for these purposes. Our assessment of deliverables and units of accounting does not change under the new accounting principles.

Pursuant to the guidance of ASU 2009-13, when a revenue arrangement contains multiple elements, such as hardware and software products, licenses and/or services, we allocate revenue to each element based on a selling price hierarchy. The selling price for a deliverable is based on its vendor-specific-objective-evidence (“VSOE”) if it is available, third-party evidence (“TPE”) if VSOE is not available, or best estimated selling price (“BESP”) if neither VSOE nor TPE is available. In multiple element arrangements where more-than-incidental software deliverables are included, revenue is allocated to each separate unit of accounting for each of the non-software deliverables and to the software deliverables as a group using the relative selling prices of each of the deliverables in the arrangement based on the aforementioned selling price hierarchy. If the arrangement contains more than one software deliverable, the arrangement consideration allocated to the software deliverables as a group is then allocated to each software deliverable using the guidance for recognizing software revenue.

As noted above, when neither VSOE nor TPE is available for a deliverable, we use BESP. We do not have significant revenue arrangements that require BESP for the three or nine months ended September 30, 2011. The inputs we use to determine the selling price of our significant deliverables include the actual price charged by the Company for a deliverable that the Company sells separately, which represents the VSOE, and the wholesale prices of the same or similar products, which represents TPE. The pattern and timing of revenue recognition for deliverables and allocation of the arrangement consideration did not change upon the adoption of the new accounting principles. Also, we do not expect the adoption of the new accounting principles to have a material effect on our financial statements in the periods after our initial adoption.

Product Sales

We recognize revenue from the sale of our products upon the transfer of title and risk of loss to our customers and once any performance obligations have been completed. Certain products are sold to customers with a street date (i.e., the earliest date these products may be sold by retailers). For these products, we recognize revenue on the later of the street date and the sale date. Revenue from product sales is recognized after deducting the estimated allowance for returns and price protection.

For our software products with online functionality, we evaluate whether those features or functionality are more than an inconsequential separate deliverable in addition to the software product. This evaluation is performed for each software product and any online transaction, such as a digital download of a title or product add-ons, when it is released.

When we determine that a software title contains online functionality that constitutes a more-than-inconsequential separate service deliverable in addition to the product, principally because of its importance to gameplay, we consider our performance obligations for this title to extend beyond the sale of the game. VSOE of fair value does not exist for the online functionality, as we do not separately charge for this component of the title. As a result, we recognize all of the software-related revenue from the sale of the title ratably over the estimated service period, which is estimated to begin the month after the later of the sale date and the street date of the title. In addition, we initially defer the costs of sales for the title (excluding intangible asset amortization), and recognize the costs of sales as the related revenues are recognized. Cost of sales includes manufacturing costs, software royalties and amortization, and intellectual property licenses costs.

We recognize revenues from World of Warcraft boxed product, expansion packs and value-added services, in each case with the related subscription service revenue, ratably over the estimated service periods beginning upon activation of the software and delivery of the related services. Revenues attributed to the sale of World of Warcraft boxed software and related expansion packs are classified as product sales and revenues attributable to subscriptions and other value-added services are classified as subscription, licensing and other revenues.

Revenues for software products with more-than-inconsequential separate service deliverables and World of Warcraft products are recognized over the estimated service periods, which range from a minimum of five months to a maximum of less than a year.

For our software products with features we consider to be incidental to the overall product offering and an inconsequential deliverable, such as products which provide limited online features at no additional cost to the consumer, we recognize the related revenue from them upon the transfer of title and risk of loss of the product to our customer.

With respect to online transactions, such as online downloads of titles or product add-ons that do not include a more-than-inconsequential separate service deliverable, revenue is recognized when the fee is paid by the online customer to purchase online content, the product is available for download and is activated for gameplay. In addition, persuasive evidence of an arrangement must exist and collection of the related receivable must be probable.

Sales incentives and other consideration given by us to our customers, such as rebates and product replacement fees, are considered adjustments of the selling price of our products and are reflected as reductions to revenue. Sales incentives and other consideration that represent costs incurred by us for assets or services received, such as the appearance of our products in a customer's national circular ad, are reflected as sales and marketing expenses when the benefit from the sales incentive is separable from sales to the same customer and we can reasonably estimate the fair value of the benefit.

Subscription Revenues

Subscription revenues are derived from World of Warcraft, a game that is playable through Blizzard's servers on a subscription-only basis. After the first month of free usage that is included with the World of Warcraft boxed software, the World of Warcraft end user may enter into a subscription agreement for additional future access. Revenues associated with the sale of subscriptions via boxed software and prepaid subscription cards, as well as prepaid subscriptions sales, are deferred until the subscription service is activated by the consumer and recognized ratably over the subscription period. Revenue from internet gaming rooms in Asia is recognized upon usage of the time packages sold. Value-added service revenues associated with subscriptions are recognized ratably over the estimated service periods.

Licensing Revenues

Third-party licensees in Russia, China and Taiwan distribute and host Blizzard's World of Warcraft game in their respective countries under license agreements with Blizzard. We receive royalties from the licensees as a result. We recognize these royalties as revenues based on the end users' activation of the underlying prepaid time, if all other performance obligations have been completed, or based on usage by the end user when we have continuing service obligations. We recognize any upfront licensing fee received over the term of the contracts.

With respect to license agreements that provide customers the right to make multiple copies in exchange for guaranteed amounts, revenue is generally recognized upon delivery of a master copy. Per copy royalties on sales that exceed the guarantee are recognized as earned. In addition, persuasive evidence of an arrangement must exist and collection of the related receivable must be probable.

Breakage Revenues

World of Warcraft boxed product sales and subscription revenues are recognized upon activation of the game. We analyze historical activation patterns over time to determine when the likelihood of activation ever occurring becomes remote. We recognize revenues from subscriptions that have not yet been activated, prepaid subscription cards, as well as prepaid subscription sales, when the likelihood of future activation occurring is remote (defined as “breakage revenues”).

Other Revenues

Other revenues primarily include licensing activity of intellectual property other than software to third-parties. Revenue is recorded upon receipt of licensee statements, or upon the receipt of cash, provided the license period has begun.