Long-term Debt (Revolving Credit Facilities Agreement) (Details) (New RCF, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
New RCF
Line of Credit Facility [Line Items]
Revolving credit aggregate amount	$ 1,200
Swing facility	250
Applicable margin of revolving credit, low rate	0.90%
Applicable margin of revolving credit, high rate	2.25%
Rate of commitment Fee on applicable margin	35.00%
Covenant terms	Under the new RCF it is required that (i) Shire’s ratio of Net Debt to EBITDA (as defined within the new RCF agreement) does not exceed 3.5 to 1 for either the 12 month period ending December 31 or June 30 unless Shire has exercised its option (which is subject to certain conditions) to increase it to 4.0 to 1 for two consecutive testing dates; (ii) the ratio of EBITDA to Net Interest (as defined in the new RCF agreement) must not be less than 4.0 to 1, for either the 12 month period ending December 31 or June 30, and (iii) additional limitations on the creation of liens, disposal of assets, incurrence of indebtedness, making of loans, giving of guarantees and granting security over assets. These financial and operating covenants have not had, and are not expected to have, an effect on the Company’s financial position and liquidity.
Arrangement costs	$ 8.0