Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2012
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies (a) Basis of preparation These interim financial statements of Shire plc and its subsidiaries (collectively “Shire” or the “Company”) and other financial information included in this Form 10-Q, are unaudited. They have been prepared in accordance with generally accepted accounting principles in the United States of America (“US GAAP”) and US Securities and Exchange Commission (“SEC”) regulations for interim reporting. The balance sheet as at December 31, 2011 was derived from audited financial statements but does not include all disclosures required by US GAAP. These interim financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company's Annual Report on Form 10-K for the year to December 31, 2011. Certain information and footnote disclosures normally included in financial statements prepared in accordance with US GAAP have been condensed or omitted from these interim financial statements. However, these interim financial statements include all adjustments, which are, in the opinion of management, necessary to fairly state the results of the interim period and the Company believes that the disclosures are adequate to make the information presented not misleading. Interim results are not necessarily indicative of results to be expected for the full year. (b) Use of estimates in interim financial statements The preparation of interim financial statements, in conformity with US GAAP and SEC regulations, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the consolidated financial statements and reported amounts of revenues and expenses during the reporting period. Estimates and assumptions are primarily made in relation to the valuation of intangible assets, the valuation of equity investments, sales deductions, income taxes (including provisions for uncertain tax positions and the realization of deferred tax assets), provisions for litigation and legal proceedings, and contingent consideration receivable from product divestments. If actual results differ from the Company's estimates, or to the extent these estimates are adjusted in future periods, the Company's results of operations could either benefit from, or be adversely affected by, any such change in estimate. (c) New accounting pronouncements Adopted during the period Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in US GAAP and International Financial Reporting Standards (“IFRS”) On January 1, 2012 the Company adopted new guidance issued by the Financial Accounting Standard Board (“FASB”) on fair value measurement and disclosure. The guidance amends the existing requirements and improves the comparability of fair value measurement and disclosure between US GAAP and IFRS. Some of the amendments clarify the application of existing fair value measurement requirements and other amendments change a particular principle or requirement for measuring fair value or for disclosing information about fair value measurements. The guidance has been adopted prospectively from January 1, 2012. The adoption of the guidance did not impact the Company's consolidated financial position, results of operations or cash flows. Enhanced disclosure of fair value measurement as required by this guidance is included in Note 14. Presentation of Comprehensive Income On January 1, 2012 the Company adopted new guidance issued by FASB on the presentation of comprehensive income, which revises the manner in which entities present comprehensive income in their financial statements. The guidance requires entities to report components of comprehensive income in either: (i) a single, continuous statement of comprehensive income; or (ii) two separate but consecutive statements. The guidance does not change those items which must be reported in other comprehensive income, and does not change the definition of net income or the calculation of earnings per share. The requirement to present the effects of reclassifications out of accumulated other comprehensive income on the components of net income and other comprehensive income for all periods presented has currently been deferred. The adoption of the guidance did not impact the Company's consolidated financial position, results of operations or cash flows. The Company has elected to present the components of comprehensive income in two separate, but consecutive statements. Enhanced disclosure of the components of comprehensive income is included in Note 12. Goodwill Impairment Testing On January 1, 2012 the Company adopted new guidance issued by FASB on the testing of goodwill for impairment. The guidance permits an entity to first assess the qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step impairment test is unnecessary. The more-likely-than-not threshold is defined as having a likelihood of more than 50 percent. An entity also has the option to bypass the qualitative assessment for any reporting unit in any period and proceed directly to performing the first step of the two-step goodwill impairment test and may resume performing the qualitative assessment in any subsequent period. The guidance has been adopted prospectively from January 1, 2012. The adoption of the guidance did not impact the Company's consolidated financial position, results of operations or cash flows.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2012

Summary of Significant Accounting Policies

1. Summary of Significant Accounting Policies

(a) Basis of preparation

These interim financial statements of Shire plc and its subsidiaries (collectively “Shire” or the “Company”) and other financial information included in this Form 10-Q, are unaudited. They have been prepared in accordance with generally accepted accounting principles in the United States of America (“US GAAP”) and US Securities and Exchange Commission (“SEC”) regulations for interim reporting.

The balance sheet as at December 31, 2011 was derived from audited financial statements but does not include all disclosures required by US GAAP.

These interim financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company's Annual Report on Form 10-K for the year to December 31, 2011.

Certain information and footnote disclosures normally included in financial statements prepared in accordance with US GAAP have been condensed or omitted from these interim financial statements. However, these interim financial statements include all adjustments, which are, in the opinion of management, necessary to fairly state the results of the interim period and the Company believes that the disclosures are adequate to make the information presented not misleading. Interim results are not necessarily indicative of results to be expected for the full year.

(b) Use of estimates in interim financial statements

The preparation of interim financial statements, in conformity with US GAAP and SEC regulations, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the consolidated financial statements and reported amounts of revenues and expenses during the reporting period. Estimates and assumptions are primarily made in relation to the valuation of intangible assets, the valuation of equity investments, sales deductions, income taxes (including provisions for uncertain tax positions and the realization of deferred tax assets), provisions for litigation and legal proceedings, and contingent consideration receivable from product divestments. If actual results differ from the Company's estimates, or to the extent these estimates are adjusted in future periods, the Company's results of operations could either benefit from, or be adversely affected by, any such change in estimate.

Adopted during the period

Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in US GAAP and International Financial Reporting Standards (“IFRS”)

On January 1, 2012 the Company adopted new guidance issued by the Financial Accounting Standard Board (“FASB”) on fair value measurement and disclosure. The guidance amends the existing requirements and improves the comparability of fair value measurement and disclosure between US GAAP and IFRS. Some of the amendments clarify the application of existing fair value measurement requirements and other amendments change a particular principle or requirement for measuring fair value or for disclosing information about fair value measurements. The guidance has been adopted prospectively from January 1, 2012. The adoption of the guidance did not impact the Company's consolidated financial position, results of operations or cash flows. Enhanced disclosure of fair value measurement as required by this guidance is included in Note 14.

Presentation of Comprehensive Income

On January 1, 2012 the Company adopted new guidance issued by FASB on the presentation of comprehensive income, which revises the manner in which entities present comprehensive income in their financial statements. The guidance requires entities to report components of comprehensive income in either: (i) a single, continuous statement of comprehensive income; or (ii) two separate but consecutive statements. The guidance does not change those items which must be reported in other comprehensive income, and does not change the definition of net income or the calculation of earnings per share. The requirement to present the effects of reclassifications out of accumulated other comprehensive income on the components of net income and other comprehensive income for all periods presented has currently been deferred.

The adoption of the guidance did not impact the Company's consolidated financial position, results of operations or cash flows. The Company has elected to present the components of comprehensive income in two separate, but consecutive statements. Enhanced disclosure of the components of comprehensive income is included in Note 12.

Goodwill Impairment Testing

On January 1, 2012 the Company adopted new guidance issued by FASB on the testing of goodwill for impairment. The guidance permits an entity to first assess the qualitative factors to determine whether the existence of events or circumstances leads to a determination that it is more likely than not that the fair value of a reporting unit is less than its carrying amount. If, after assessing the totality of events or circumstances, an entity determines it is not more likely than not that the fair value of a reporting unit is less than its carrying amount, then performing the two-step impairment test is unnecessary. The more-likely-than-not threshold is defined as having a likelihood of more than 50 percent. An entity also has the option to bypass the qualitative assessment for any reporting unit in any period and proceed directly to performing the first step of the two-step goodwill impairment test and may resume performing the qualitative assessment in any subsequent period. The guidance has been adopted prospectively from January 1, 2012. The adoption of the guidance did not impact the Company's consolidated financial position, results of operations or cash flows.