Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Schedule of Calculation of Numerator and Denominator in Earnings Per Share
Numerator for basic earnings per share	$ 64.8		$ 238.4
Interest on convertible bonds, net of tax	0	[1]	8.4	[1]
Numerator for diluted earnings per share	$ 64.8		$ 246.8
Schedule of Weighted Average Number of Shares
Basic	551.5	[2]	553.5	[2]
Effect of dilutive shares:
Share based awards to employees	3.8	[3]	8.6	[3]
Convertible bonds 2.75% due 2014	0	[4]	33.5	[4]
Diluted	555.3		595.6
Earning per ordinary share - basic
Earnings per ordinary share attributable to Shire plc shareholders - basic	$ 0.117		$ 0.431
Earnings per ordinary share - diluted
Earnings per ordinary share attributable to Shire plc shareholders - diluted	$ 0.117		$ 0.414
Share Awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	5.6	[5]	6.1	[5]
Convertible bonds 2.75% due 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	33.6	[6]	0	[6]

[1] 1. For the three months ended March 31, 2013 interest on convertible bonds has not been added back as the effect would be anti-dilutive.

[2] Excludes shares purchased by the EBT and under the share buy-back program and presented by Shire as treasury stock.

[3] Calculated using the treasury stock method.

[4] Calculated using the ‘if-converted’ method.

[5] Certain stock options have been excluded from the calculation of diluted EPS because (a) their exercise prices exceeded Shire plc’s average share price during the calculation period or (b) the required performance conditions were not satisfied as at the balance sheet date.

[6] For the three months period to March 31, 2013 the ordinary shares underlying the convertible bonds have not been included in the calculation of the diluted weighted average number of shares, as the effect of their inclusion would be anti-dilutive.