Convertible Bonds (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Mar. 11, 2011	Mar. 11, 2009	May 09, 2007
Debt Instrument [Line Items]
Principal amount	$ 1,100
Stated interest rate	2.75%
Issuance price to principal amount, percent	100.00%
Shire 2.75% Convertible Bond due 2014
Debt Instrument [Line Items]
Debt issuance date	May 09, 2007
Principal amount	$ 1,100
Stated interest rate	2.75%
Final maturity date	May 09, 2014
Repayment terms	The Bonds may be redeemed at the option of the Company, at their principal amount together with accrued and unpaid interest if: (i) at any time after May 23, 2012 if on no less than 20 dealing days in any period of 30 consecutive dealing days the value of Shire’s ordinary shares underlying each Bond in the principal amount of $100,000 would exceed $130,000; or (ii) at any time conversion rights have been exercised, and/or purchases and corresponding cancellations, and/or redemptions effected in respect of 85% or more in principal amount of Bonds originally issued. The bonds may also be redeemed at the option of the bond holder at their principal amount including accrued and unpaid interest on May 9, 2012 (the “Put Option”), or following occurrence of a change of control of Shire. The Bonds are repayable in US dollars, but also contain provisions entitling the Company to settle redemption amounts in Pounds sterling, or in the case of the Final Maturity Date and or any change of control Shire, by delivery of the underlying ordinary shares and a cash top-up amount. On April 9, 2012 the deadline for Bondholders to choose to exercise their Put Option on May 9, 2012 passed. No elections from the Bondholders were received by this date and the Bonds are now due on the Final Maturity Date, subject to the exceptions above. As the Company is no longer required to redeem the Bonds within twelve months of the balance sheet date, the Bonds have been presented as a non-current liability at December 31, 2012.
Conversion price				$ 33.5879
Adjusted conversion price		$ 32.83	$ 33.17