Business Combinations (Acquisition of Baxalta) (Narrative) (Details) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended								12 Months Ended
	Jun. 03, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Revenues		$ 4,144.9	$ 3,697.6	$ 3,745.8	$ 3,572.3	$ 3,806.1	$ 3,452.1	$ 2,429.1	$ 1,709.3	$ 15,160.6	$ 11,396.6	$ 6,416.7
Goodwill		19,831.7				$ 17,888.2				19,831.7	17,888.2	4,147.8
Integration and acquisition costs										$ 894.5	883.9	$ 39.8
Minimum
Business Acquisition [Line Items]
Estimated useful life of intangible assets										1 year
Maximum
Business Acquisition [Line Items]
Estimated useful life of intangible assets										24 years
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
Revenues											$ 4,011.6
Cost of sales adjustment										$ 85.2
Amortization adjustment										23.3
Goodwill	$ 12,498.6	12,498.6								12,498.6
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
Integration and acquisition costs										763.9
Baxalta | Currently marketed products
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
Baxalta | In-Process Research and Development (IPR&D)
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%
Baxalta | Minimum | Currently marketed products
Business Acquisition [Line Items]
Estimated useful life of intangible assets	6 years
Baxalta | Maximum | Currently marketed products
Business Acquisition [Line Items]
Estimated useful life of intangible assets	23 years
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