Guarantor Financial Information (Consolidating Statements of Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Total revenues	$ 3,871.7	$ 3,697.6	$ 11,556.9	$ 11,015.7
Costs and expenses:
Cost of sales	1,157.6	1,001.4	3,398.3	3,437.3
Research and development	407.2	402.8	1,240.0	1,324.5
Selling, general and administrative	836.8	859.7	2,549.3	2,647.7
Amortization of acquired intangible assets	433.7	482.4	1,375.3	1,280.5
Integration and acquisition costs	93.0	237.0	512.0	696.7
Reorganization costs	254.8	5.4	268.9	24.5
Gain on sale of Oncology franchise	(267.2)	0.3	(267.2)	(0.4)
Total operating expenses	2,915.9	2,989.0	9,076.6	9,410.8
Operating income from continuing operations	955.8	708.6	2,480.3	1,604.9
Interest income/(expense), net	(123.9)	(140.3)	(373.3)	(419.7)
Other income/(expense), net	(96.1)	(0.2)	(43.9)	6.8
Total other expense, net	(220.0)	(140.5)	(417.2)	(412.9)
Income from continuing operations before income taxes and equity in earnings of equity method investees	735.8	568.1	2,063.1	1,192.0
Income taxes	(203.3)	(13.5)	(371.0)	(44.6)
Equity in income/(losses) of equity method investees, net of taxes	4.7	(3.4)	11.2	0.1
Income from continuing operations, net of taxes	537.2	551.2	1,703.3	1,147.5
Gain (loss) from discontinued operations, net of taxes	0.0	(0.4)	0.0	18.6
Net income	537.2	550.8	1,703.3	1,166.1
Comprehensive income/(loss)	436.0	1,319.8	954.7	3,632.8
Eliminations
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Costs and expenses:
Cost of sales	0.0	0.0	0.0	0.0
Research and development	0.0	0.0	0.0	0.0
Selling, general and administrative	0.0	0.0	0.0	0.0
Amortization of acquired intangible assets	0.0	0.0	0.0	0.0
Integration and acquisition costs	0.0	0.0	0.0	0.0
Reorganization costs	0.0	0.0	0.0	0.0
Gain on sale of Oncology franchise	0.0	0.0		0.0
Total operating expenses	0.0	0.0	0.0	0.0
Operating income from continuing operations	0.0	0.0	0.0	0.0
Interest income/(expense), net	0.0	0.0	0.0	0.0
Other income/(expense), net	0.0	0.0	0.0	0.0
Total other expense, net	0.0	0.0	0.0	0.0
Income from continuing operations before income taxes and equity in earnings of equity method investees	0.0	0.0	0.0	0.0
Income taxes	0.0	0.0	0.0	0.0
Equity in income/(losses) of equity method investees, net of taxes	(536.8)	(524.3)	(2,258.6)	(1,340.9)
Income from continuing operations, net of taxes	(536.8)	(524.3)	(2,258.6)	(1,340.9)
Gain (loss) from discontinued operations, net of taxes		0.0		0.0
Net income	(536.8)	(524.3)	(2,258.6)	(1,340.9)
Comprehensive income/(loss)	(341.5)	(1,995.8)	(829.8)	(6,130.6)
Shire plc (Parent Guarantor)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Costs and expenses:
Cost of sales	0.0	0.0	0.0	0.0
Research and development	0.0	0.0	0.0	0.0
Selling, general and administrative	(14.5)	6.1	76.4	24.2
Amortization of acquired intangible assets	0.0	0.0	0.0	0.0
Integration and acquisition costs	45.0	0.0	142.7	164.7
Reorganization costs	0.0	0.0	0.0	0.0
Gain on sale of Oncology franchise	0.0	0.0	0.0	0.0
Total operating expenses	30.5	6.1	219.1	188.9
Operating income from continuing operations	(30.5)	(6.1)	(219.1)	(188.9)
Interest income/(expense), net	(43.7)	(48.0)	(110.4)	(109.1)
Other income/(expense), net	0.2	0.0	0.0	1.8
Total other expense, net	(43.5)	(48.0)	(110.4)	(107.3)
Income from continuing operations before income taxes and equity in earnings of equity method investees	(74.0)	(54.1)	(329.5)	(296.2)
Income taxes	0.2	0.9	17.4	1.7
Equity in income/(losses) of equity method investees, net of taxes	611.0	604.0	2,015.4	1,460.6
Income from continuing operations, net of taxes	537.2	550.8	1,703.3	1,166.1
Gain (loss) from discontinued operations, net of taxes		0.0		0.0
Net income	537.2	550.8	1,703.3	1,166.1
Comprehensive income/(loss)	436.0	1,319.8	954.7	3,632.8
SAIIDAC (SAIIDAC Notes Subsidiary Issuer)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Costs and expenses:
Cost of sales	0.0	0.0	0.0	0.0
Research and development	0.0	0.0	0.0	0.0
Selling, general and administrative	0.0	0.0	0.0	0.0
Amortization of acquired intangible assets	0.0	0.0	0.0	0.0
Integration and acquisition costs	0.0	0.0	0.0	0.0
Reorganization costs	0.0	0.0	0.0	0.0
Gain on sale of Oncology franchise	0.0	0.0	0.0	0.0
Total operating expenses	0.0	0.0	0.0	0.0
Operating income from continuing operations	0.0	0.0	0.0	0.0
Interest income/(expense), net	5.6	3.0	(2.2)	14.5
Other income/(expense), net	0.0	0.0	0.0	0.0
Total other expense, net	5.6	3.0	(2.2)	14.5
Income from continuing operations before income taxes and equity in earnings of equity method investees	5.6	3.0	(2.2)	14.5
Income taxes	(2.4)	0.6	0.6	(3.6)
Equity in income/(losses) of equity method investees, net of taxes	0.0	0.0	0.0	0.0
Income from continuing operations, net of taxes	3.2	3.6	(1.6)	10.9
Gain (loss) from discontinued operations, net of taxes		0.0		0.0
Net income	3.2	3.6	(1.6)	10.9
Comprehensive income/(loss)	3.2	3.6	(1.6)	10.9
Baxalta Inc. (Baxalta Notes Subsidiary Issuer and SAIIDAC Notes Subsidiary Guarantor)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Costs and expenses:
Cost of sales	0.0	0.0	0.0	0.0
Research and development	0.0	0.0	0.0	0.0
Selling, general and administrative	0.0	4.0	7.2	15.3
Amortization of acquired intangible assets	0.0	0.0	0.0	0.0
Integration and acquisition costs	5.3	9.2	7.4	52.3
Reorganization costs	0.0	0.0	0.0	0.0
Gain on sale of Oncology franchise	0.0	0.0	0.0	0.0
Total operating expenses	5.3	13.2	14.6	67.6
Operating income from continuing operations	(5.3)	(13.2)	(14.6)	(67.6)
Interest income/(expense), net	(37.1)	(23.6)	(91.6)	(66.5)
Other income/(expense), net	(24.8)	4.4	(23.9)	4.3
Total other expense, net	(61.9)	(19.2)	(115.5)	(62.2)
Income from continuing operations before income taxes and equity in earnings of equity method investees	(67.2)	(32.4)	(130.1)	(129.8)
Income taxes	15.2	(8.9)	28.4	(45.0)
Equity in income/(losses) of equity method investees, net of taxes	(74.2)	(79.8)	243.2	(119.7)
Income from continuing operations, net of taxes	(126.2)	(121.1)	141.5	(294.5)
Gain (loss) from discontinued operations, net of taxes		0.0		0.0
Net income	(126.2)	(121.1)	141.5	(294.5)
Comprehensive income/(loss)	(220.3)	581.0	(538.7)	2,031.5
Non-Guarantor Non-Issuer Subsidiaries
Revenues:
Total revenues	3,871.7	3,697.6	11,556.9	11,015.7
Costs and expenses:
Cost of sales	1,157.6	1,001.4	3,398.3	3,437.3
Research and development	407.2	402.8	1,240.0	1,324.5
Selling, general and administrative	851.3	849.6	2,465.7	2,608.2
Amortization of acquired intangible assets	433.7	482.4	1,375.3	1,280.5
Integration and acquisition costs	42.7	227.8	361.9	479.7
Reorganization costs	254.8	5.4	268.9	24.5
Gain on sale of Oncology franchise		0.3		(0.4)
Total operating expenses	2,880.1	2,969.7	8,842.9	9,154.3
Operating income from continuing operations	991.6	727.9	2,714.0	1,861.4
Interest income/(expense), net	(48.7)	(71.7)	(169.1)	(258.6)
Other income/(expense), net	(71.5)	(4.6)	(20.0)	0.7
Total other expense, net	(120.2)	(76.3)	(189.1)	(257.9)
Income from continuing operations before income taxes and equity in earnings of equity method investees	871.4	651.6	2,524.9	1,603.5
Income taxes	(216.3)	(6.1)	(417.4)	2.3
Equity in income/(losses) of equity method investees, net of taxes	4.7	(3.3)	11.2	0.1
Income from continuing operations, net of taxes	659.8	642.2	2,118.7	1,605.9
Gain (loss) from discontinued operations, net of taxes		(0.4)		18.6
Net income	659.8	641.8	2,118.7	1,624.5
Comprehensive income/(loss)	558.6	1,411.2	1,370.1	4,088.2
Non-Guarantor Subsidiaries of Baxalta Notes
Revenues:
Total revenues	3,871.7	3,697.6	11,556.9	11,015.7
Costs and expenses:
Cost of sales	1,157.6	1,001.4	3,398.3	3,437.3
Research and development	407.2	402.8	1,240.0	1,324.5
Selling, general and administrative	851.3	849.6	2,465.7	2,608.2
Amortization of acquired intangible assets	433.7	482.4	1,375.3	1,280.5
Integration and acquisition costs	42.7	227.8	361.9	479.7
Reorganization costs	254.8	5.4	268.9	24.5
Gain on sale of Oncology franchise	(267.2)	0.3	(267.2)	(0.4)
Total operating expenses	2,880.1	2,969.7	8,842.9	9,154.3
Operating income from continuing operations	991.6	727.9	2,714.0	1,861.4
Interest income/(expense), net	(43.1)	(68.7)	(171.3)	(244.1)
Other income/(expense), net	(71.5)	(4.6)	(20.0)	0.7
Total other expense, net	(114.6)	(73.3)	(191.3)	(243.4)
Income from continuing operations before income taxes and equity in earnings of equity method investees	877.0	654.6	2,522.7	1,618.0
Income taxes	(218.7)	(5.5)	(416.8)	(1.3)
Equity in income/(losses) of equity method investees, net of taxes	4.7	(3.3)	11.2	0.1
Income from continuing operations, net of taxes	663.0	645.8	2,117.1	1,616.8
Gain (loss) from discontinued operations, net of taxes		(0.4)		18.6
Net income	663.0	645.4	2,117.1	1,635.4
Comprehensive income/(loss)	561.8	1,414.8	1,368.5	4,099.1
Product sales
Revenues:
Total revenues	3,752.8	3,533.8	11,198.5	10,537.9
Product sales | Eliminations
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Product sales | Shire plc (Parent Guarantor)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Product sales | SAIIDAC (SAIIDAC Notes Subsidiary Issuer)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Product sales | Baxalta Inc. (Baxalta Notes Subsidiary Issuer and SAIIDAC Notes Subsidiary Guarantor)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Product sales | Non-Guarantor Non-Issuer Subsidiaries
Revenues:
Total revenues	3,752.8	3,533.8	11,198.5	10,537.9
Product sales | Non-Guarantor Subsidiaries of Baxalta Notes
Revenues:
Total revenues	3,752.8	3,533.8	11,198.5	10,537.9
Royalties and other revenues
Revenues:
Total revenues	118.9	163.8	358.4	477.8
Royalties and other revenues | Eliminations
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Royalties and other revenues | Shire plc (Parent Guarantor)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Royalties and other revenues | SAIIDAC (SAIIDAC Notes Subsidiary Issuer)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Royalties and other revenues | Baxalta Inc. (Baxalta Notes Subsidiary Issuer and SAIIDAC Notes Subsidiary Guarantor)
Revenues:
Total revenues	0.0	0.0	0.0	0.0
Royalties and other revenues | Non-Guarantor Non-Issuer Subsidiaries
Revenues:
Total revenues	118.9	163.8	358.4	477.8
Royalties and other revenues | Non-Guarantor Subsidiaries of Baxalta Notes
Revenues:
Total revenues	$ 118.9	$ 163.8	$ 358.4	$ 477.8