Guarantor Financial Information (Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided/(used in) by operating activities	$ 2,737.1	$ 1,506.0
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	0.0	0.0
Purchases of businesses, net of cash acquired	0.0	(17,476.2)
Purchases of PP&E and non-current investments	(565.5)	(402.5)
Proceeds from disposal of non-current investments		0.6
(Payment)/proceeds from sale of investments	48.1
Movements in restricted cash	(8.6)	68.3
Other, net	34.8	(1.5)
Net cash used in investing activities	(491.2)	(17,811.3)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	3,261.6	31,742.3
Repayment of revolving line of credit, long term and short term borrowings	(5,664.5)	(14,632.9)
Proceeds from/to intercompany borrowings	0.0	0.0
Payment of dividend	(234.7)	(130.2)
Debt issuance costs		(171.0)
Proceeds from exercise of options	92.2	137.2
Other, net	(26.2)	(44.8)
Net cash (used in)/provided by financing activities	(2,571.6)	16,900.6
Effect of foreign exchange rate changes on cash and cash equivalents	6.2	(2.2)
Net (decrease)/increase in cash and cash equivalents	(319.5)	593.1
Cash and cash equivalents at beginning of period	528.8	135.5
Cash and cash equivalents at end of period	209.3	728.6
Eliminations
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided/(used in) by operating activities	0.0	0.0
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	6,470.6	23,425.7
Purchases of businesses, net of cash acquired		0.0
Purchases of PP&E and non-current investments	0.0	0.0
Proceeds from disposal of non-current investments		0.0
(Payment)/proceeds from sale of investments	0.0
Movements in restricted cash	0.0	0.0
Other, net	0.0	0.0
Net cash used in investing activities	6,470.6	23,425.7
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/to intercompany borrowings	(6,470.6)	(23,425.7)
Payment of dividend	0.0	0.0
Debt issuance costs		0.0
Proceeds from exercise of options	0.0	0.0
Other, net	0.0	0.0
Net cash (used in)/provided by financing activities	(6,470.6)	(23,425.7)
Effect of foreign exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease)/increase in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0
Shire plc (Parent Guarantor)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided/(used in) by operating activities	(102.9)	(79.8)
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(1,339.3)	(2,390.0)
Purchases of businesses, net of cash acquired		0.0
Purchases of PP&E and non-current investments	0.0	0.0
Proceeds from disposal of non-current investments		0.0
(Payment)/proceeds from sale of investments	0.0
Movements in restricted cash	0.0	0.0
Other, net	0.0	0.0
Net cash used in investing activities	(1,339.3)	(2,390.0)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	2,110.0	1,655.0
Repayment of revolving line of credit, long term and short term borrowings	(2,560.0)	(2,215.8)
Proceeds from/to intercompany borrowings	1,919.6	3,045.3
Payment of dividend	(27.6)	(15.0)
Debt issuance costs		0.0
Proceeds from exercise of options	0.2	0.3
Other, net	0.0	0.0
Net cash (used in)/provided by financing activities	1,442.2	2,469.8
Effect of foreign exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease)/increase in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0
SAIIDAC (SAIIDAC Notes Subsidiary Issuer)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided/(used in) by operating activities	(62.9)	182.3
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(262.9)	(18,172.0)
Purchases of businesses, net of cash acquired		0.0
Purchases of PP&E and non-current investments	0.0	0.0
Proceeds from disposal of non-current investments		0.0
(Payment)/proceeds from sale of investments	0.0
Movements in restricted cash	0.0	0.0
Other, net	0.0	0.0
Net cash used in investing activities	(262.9)	(18,172.0)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	1,150.0	30,079.9
Repayment of revolving line of credit, long term and short term borrowings	(3,100.0)	(12,409.2)
Proceeds from/to intercompany borrowings	2,275.8	490.0
Payment of dividend	0.0	0.0
Debt issuance costs		(171.0)
Proceeds from exercise of options	0.0	0.0
Other, net	0.0	0.0
Net cash (used in)/provided by financing activities	325.8	17,989.7
Effect of foreign exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease)/increase in cash and cash equivalents	0.0	0.0
Cash and cash equivalents at beginning of period	0.0	0.0
Cash and cash equivalents 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/(used in) by operating activities	0.6	(51.8)
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(659.3)	0.0
Purchases of businesses, net of cash acquired		0.0
Purchases of PP&E and non-current investments	0.0	(6.0)
Proceeds from disposal of non-current investments		0.0
(Payment)/proceeds from sale of investments	(9.8)
Movements in restricted cash	0.0	0.0
Other, net	0.0	0.0
Net cash used in investing activities	(669.1)	(6.0)
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/to intercompany borrowings	623.9	308.4
Payment of dividend	0.0	0.0
Debt issuance costs		0.0
Proceeds from exercise of options	4.6	126.2
Other, net	(0.8)	(68.2)
Net cash (used in)/provided by financing activities	627.7	366.4
Effect of foreign exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease)/increase in cash and cash equivalents	(40.8)	308.6
Cash and cash equivalents at beginning of period	41.7	0.0
Cash and cash equivalents at end of period	0.9	308.6
Non-Guarantor Non-Issuer Subsidiaries
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided/(used in) by operating activities	2,902.3	1,455.3
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(4,209.1)	(2,863.7)
Purchases of businesses, net of cash acquired		(17,476.2)
Purchases of PP&E and non-current investments	(565.5)	(396.5)
Proceeds from disposal of non-current investments		0.6
(Payment)/proceeds from sale of investments	57.9
Movements in restricted cash	(8.6)	68.3
Other, net	34.8	(1.5)
Net cash used in investing activities	(4,690.5)	(20,669.0)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	1.6	7.4
Repayment of revolving line of credit, long term and short term borrowings	(4.5)	(7.9)
Proceeds from/to intercompany borrowings	1,651.3	19,582.0
Payment of dividend	(207.1)	(115.2)
Debt issuance costs		0.0
Proceeds from exercise of options	87.4	10.7
Other, net	(25.4)	23.4
Net cash (used in)/provided by financing activities	1,503.3	19,500.4
Effect of foreign exchange rate changes on cash and cash equivalents	6.2	(2.2)
Net (decrease)/increase in cash and cash equivalents	(278.7)	284.5
Cash and cash equivalents at beginning of period	487.1	135.5
Cash and cash equivalents at end of period	208.4	420.0
Non-Guarantor Subsidiaries of Baxalta Notes
CASH FLOWS FROM OPERATING ACTIVITIES:
Net cash provided/(used in) by operating activities	2,839.4	1,637.6
CASH FLOWS FROM INVESTING ACTIVITIES:
Transactions with subsidiaries	(4,472.0)	(21,035.7)
Purchases of businesses, net of cash acquired		(17,476.2)
Purchases of PP&E and non-current investments	(565.5)	(396.5)
Proceeds from disposal of non-current investments		0.6
(Payment)/proceeds from sale of investments	57.9
Movements in restricted cash	(8.6)	68.3
Other, net	34.8	(1.5)
Net cash used in investing activities	(4,953.4)	(38,841.0)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit, long term and short term borrowings	1,151.6	30,087.3
Repayment of revolving line of credit, long term and short term borrowings	(3,104.5)	(12,417.1)
Proceeds from/to intercompany borrowings	3,927.1	20,072.0
Payment of dividend	(207.1)	(115.2)
Debt issuance costs		(171.0)
Proceeds from exercise of options	87.4	10.7
Other, net	(25.4)	23.4
Net cash (used in)/provided by financing activities	1,829.1	37,490.1
Effect of foreign exchange rate changes on cash and cash equivalents	6.2	(2.2)
Net (decrease)/increase in cash and cash equivalents	(278.7)	284.5
Cash and cash equivalents at beginning of period	487.1	135.5
Cash and cash equivalents at end of period	$ 208.4	$ 420.0