Business Combinations (Acquisition of Baxalta) (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
	Jun. 03, 2016 USD ($) $ / shares shares	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 19,482.1	$ 12,962.4	$ 19,482.1	$ 12,962.4	$ 17,888.2	$ 4,147.8
Integration and acquisition costs		343.7	$ 363.0	459.7	$ 454.1
Baxalta
Business Acquisition [Line Items]
Purchase price paid per share of acquiree, in cash (in USD per share) | $ / shares	$ 18.00
Shares issued for acquisition (in shares) | shares	305.2
Cost of sales adjustment				85.2
Amortization adjustment				23.3
Goodwill	$ 12,498.6	12,498.6		12,498.6
Integration and acquisition costs		192.4		310.9
Maximum amount of contingent cash consideration	1,500.0
Contingent consideration payable	165.0
Defined benefit net liability	610.4
Fair value of plan assets	$ 358.5
Baxalta | ADS
Business Acquisition [Line Items]
Shire shares per Baxalta share	0.1482
Baxalta | Common stock
Business Acquisition [Line Items]
Shire shares per Baxalta share	0.4446
Currently marketed products | Baxalta
Business Acquisition [Line Items]
Intangible assets	$ 21,165.0	21,165.0		21,165.0
Weighted average amortization period of acquired amortizable intangible assets	21 years
In-Process Research and Development (IPR&D) | Baxalta
Business Acquisition [Line Items]
Intangible assets	$ 160.0	$ 160.0		$ 160.0
Discount rate used in determining fair value of acquired in process research and development, low rate	9.50%
Minimum | Currently marketed products | Baxalta
Business Acquisition [Line Items]
Estimated useful life of intangible assets	6 years
Maximum | Currently marketed products | Baxalta
Business Acquisition [Line Items]
Estimated useful life of intangible assets	23 years