Guarantor Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	$ 1,010.3	$ 459.1
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	0.0	0.0
Purchases of PP&E	(177.8)	(212.5)
Other, net	(11.1)	1.2
Net cash used in investing activities	(188.9)	(211.3)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	423.3	1,401.9
Repayment of revolving line of credit, long term and short term borrowings	(1,439.4)	(1,825.7)
Proceeds from intercompany borrowings	0.0	0.0
Proceeds from issuance of stock for share-based compensation arrangements	40.5	42.1
Other, net	(6.5)	(20.1)
Net cash used in financing activities	(982.1)	(401.8)
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	2.1	2.7
Net decrease in cash and cash equivalents and restricted cash	(158.6)	(151.3)
Cash and cash equivalents and restricted cash at beginning of period	511.8	554.4
Cash and cash equivalents and restricted cash at end of period	353.2	403.1
Eliminations
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	0.0	0.0
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	2,677.0	1,604.3
Purchases of PP&E	0.0	0.0
Other, net	0.0	0.0
Net cash used in investing activities	2,677.0	1,604.3
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	0.0	0.0
Repayment of revolving line of credit, long term and short term borrowings	0.0	0.0
Proceeds from intercompany borrowings	(2,677.0)	(1,604.3)
Proceeds from issuance of stock for share-based compensation arrangements	0.0	0.0
Other, net	0.0	0.0
Net cash used in financing activities	(2,677.0)	(1,604.3)
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	0.0	0.0
Net decrease in cash and cash equivalents and restricted cash	0.0	0.0
Cash and cash equivalents and restricted cash at beginning of period	0.0	0.0
Cash and cash equivalents and restricted cash at end of period	0.0	0.0
Shire plc (Parent Guarantor)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	(4.6)	(9.6)
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	0.0	(760.6)
Purchases of PP&E	0.0	0.0
Other, net	0.0	0.3
Net cash used in investing activities	0.0	(760.3)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	0.0	1,400.0
Repayment of revolving line of credit, long term and short term borrowings	0.0	(820.0)
Proceeds from intercompany borrowings	4.5	189.8
Proceeds from issuance of stock for share-based compensation arrangements	0.1	0.1
Other, net	0.0	0.0
Net cash used in financing activities	4.6	769.9
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	0.0	0.0
Net decrease in cash and cash equivalents and restricted cash	0.0	0.0
Cash and cash equivalents and restricted cash at beginning of period	0.0	0.0
Cash and cash equivalents and restricted cash at end of period	0.0	0.0
SAIIDAC (SAIIDAC Notes Subsidiary Issuer)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	(0.5)	(84.1)
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(584.7)	0.0
Purchases of PP&E	0.0	0.0
Other, net	0.0	0.0
Net cash used in investing activities	(584.7)	0.0
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	75.0	0.0
Repayment of revolving line of credit, long term and short term borrowings	(1,110.0)	(1,000.0)
Proceeds from intercompany borrowings	1,620.2	1,084.1
Proceeds from issuance of stock for share-based compensation arrangements	0.0	0.0
Other, net	0.0	0.0
Net cash used in financing activities	585.2	84.1
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	0.0	0.0
Net decrease in cash and cash equivalents and restricted cash	0.0	0.0
Cash and cash equivalents and restricted cash at beginning of period	0.0	0.0
Cash and cash equivalents and restricted cash at end of period	0.0	0.0
Baxalta Inc. (Baxalta Notes Subsidiary Issuer and SAIIDAC Notes Subsidiary Guarantor)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	(5.6)	(0.3)
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(233.9)	(110.5)
Purchases of PP&E	1.9	(2.4)
Other, net	0.1	2.0
Net cash used in investing activities	(231.9)	(110.9)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	0.0	0.0
Repayment of revolving line of credit, long term and short term borrowings	0.0	0.0
Proceeds from intercompany borrowings	233.7	69.3
Proceeds from issuance of stock for share-based compensation arrangements	3.3	2.9
Other, net	0.0	(2.4)
Net cash used in financing activities	237.0	69.8
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	0.0	0.0
Net decrease in cash and cash equivalents and restricted cash	(0.5)	(41.4)
Cash and cash equivalents and restricted cash at beginning of period	0.5	41.7
Cash and cash equivalents and restricted cash at end of period	0.0	0.3
Non-Guarantor Non-Issuer Subsidiaries
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	1,021.0	553.1
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(1,858.4)	(733.2)
Purchases of PP&E	(179.7)	(210.1)
Other, net	(11.2)	(1.1)
Net cash used in investing activities	(2,049.3)	(944.4)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	348.3	1.9
Repayment of revolving line of credit, long term and short term borrowings	(329.4)	(5.7)
Proceeds from intercompany borrowings	818.6	261.1
Proceeds from issuance of stock for share-based compensation arrangements	37.1	39.1
Other, net	(6.5)	(17.7)
Net cash used in financing activities	868.1	278.7
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	2.1	2.7
Net decrease in cash and cash equivalents and restricted cash	(158.1)	(109.9)
Cash and cash equivalents and restricted cash at beginning of period	511.3	512.7
Cash and cash equivalents and restricted cash at end of period	353.2	402.8
Non-Guarantor Subsidiaries of Baxalta Notes
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided by/(used in) operating activities	1,020.5	469.0
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(2,443.1)	(733.2)
Purchases of PP&E	(179.7)	(210.1)
Other, net	(11.2)	(1.1)
Net cash used in investing activities	(2,634.0)	(944.4)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	423.3	1.9
Repayment of revolving line of credit, long term and short term borrowings	(1,439.4)	(1,005.7)
Proceeds from intercompany borrowings	2,438.8	1,345.2
Proceeds from issuance of stock for share-based compensation arrangements	37.1	39.1
Other, net	(6.5)	(17.7)
Net cash used in financing activities	1,453.3	362.8
Effect of foreign exchange rate changes on cash and cash equivalents and restricted cash	2.1	2.7
Net decrease in cash and cash equivalents and restricted cash	(158.1)	(109.9)
Cash and cash equivalents and restricted cash at beginning of period	511.3	512.7
Cash and cash equivalents and restricted cash at end of period	$ 353.2	$ 402.8