Comprehensive Earnings (Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	$ (89.5)	$ (76.6)
Net unrealized gain on marketable securities, net of tax	0.4		$ 0.0
Net unrecognized losses and prior service cost related to defined benefit plans, net of tax	(1.6)		1.7
Foreign currency translation adjustment	(1,597.5)		(1,259.0)
Other comprehensive (loss) earnings, before tax	(253.8)	166.0
Net unrealized (loss) gain on marketable securities	0.4	(0.4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	(0.2)	4.3
Sales Revenue, Goods, Net	2,460.6	2,650.4
Interest expense	131.2	131.7
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	11,891.6	13,170.1	12,167.1	$ 13,307.6
Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrecognized gain (loss) on derivatives	26.0	(32.0)
Net Investment Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulate Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Net Investment Hedges, Effect Net of Taxx	(75.7)		(130.9)
Net unrecognized gain (loss) on derivatives	58.1	(59.2)
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit		(11.2)
Accumulated other comprehensive loss	(1,710.5)	(191.5)			$ (361.2)
Other comprehensive earnings (loss) before reclassifications, before tax	(255.4)	168.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(191.5)	(1,441.3)	$ (361.2)
Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit		(10.6)
Net unrecognized losses on derivatives in cash flow hedging relationships, net of tax		(22.6)			(3.7)
Other comprehensive earnings (loss) before reclassifications, before tax		(29.1)
Gains and Losses on Derivatives | Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	8.8
Cumulative Effect of New Accounting Principle in Period of Adoption	(3.4)	2.5
Net unrecognized losses on derivatives in cash flow hedging relationships, net of tax	(39.3)		(53.1)
Other comprehensive earnings (loss) before reclassifications, before tax	24.5
Gains and Losses on Derivatives | Net Investment Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	2.9	0.0
Cumulative Effect of New Accounting Principle in Period of Adoption	0.0	0.0
Net unrecognized losses on derivatives in cash flow hedging relationships, net of tax		(299.0)			(239.8)
Other comprehensive earnings (loss) before reclassifications, before tax		(59.2)
Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit		(0.1)
Net unrealized gain on marketable securities, net of tax		(0.2)			10.1
Other comprehensive earnings (loss) before reclassifications, before tax		(0.4)
Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit		0.5
Net unrecognized losses and prior service cost related to defined benefit plans, net of tax		2.2			6.0
Other comprehensive earnings (loss) before reclassifications, before tax	0.1	(4.4)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit		0.0
Foreign currency translation adjustment		128.1			$ (133.8)
Other comprehensive earnings (loss) before reclassifications, before tax	(338.5)
Reclassification out of Accumulated Other Comprehensive Earnings | AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	11.8
Cumulative Effect of New Accounting Principle in Period of Adoption	(3.6)	(7.5)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	(0.3)	(0.1)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	0.2
Reclassification out of Accumulated Other Comprehensive Earnings | Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrecognized gain (loss) on derivatives		(32.0)
Reclassification out of Accumulated Other Comprehensive Earnings | Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	0.0
Cumulative Effect of New Accounting Principle in Period of Adoption	0.0	(10.0)
Net unrealized (loss) gain on marketable securities		(0.4)
Reclassification out of Accumulated Other Comprehensive Earnings | Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	0.1
Cumulative Effect of New Accounting Principle in Period of Adoption	(0.2)	0.0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax		4.3
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax		0.1
Reclassification out of Accumulated Other Comprehensive Earnings | Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	0.0
Cumulative Effect of New Accounting Principle in Period of Adoption	0.0	0.0
Other comprehensive (loss) earnings, before tax		261.9
Mylan N.V.
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	(5.6)	(7.3)
Other comprehensive (loss) earnings, before tax	(253.8)	166.0
Net unrealized (loss) gain on marketable securities	0.4	(0.4)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	(0.2)	4.3
Sales Revenue, Goods, Net	0.0	0.0
Interest expense	81.7	93.5
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	11,891.6		$ 12,167.1
Mylan N.V. | Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrecognized gain (loss) on derivatives	26.0	(32.0)
Mylan N.V. | Net Investment Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrecognized gain (loss) on derivatives	58.1	(59.2)
Foreign currency forward contracts | Gains and Losses on Derivatives | Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Sales Revenue, Goods, Net	(0.3)
Foreign currency forward contracts | Reclassification out of Accumulated Other Comprehensive Earnings | AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Sales Revenue, Goods, Net	(0.3)	(4.8)
Foreign currency forward contracts | Reclassification out of Accumulated Other Comprehensive Earnings | Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Sales Revenue, Goods, Net	(0.3)	(4.8)
Interest rate swaps | Gains and Losses on Derivatives | Cash Flow Hedging
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	1.8
Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Earnings | AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	1.8	1.9
Interest rate swaps | Reclassification out of Accumulated Other Comprehensive Earnings | Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest expense	1.8	1.9
Pension and other postretirement benefits
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	(0.3)	(0.1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0.2
Pension and other postretirement benefits | Reclassification out of Accumulated Other Comprehensive Earnings | Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, before Tax	$ (0.3)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		$ 0.0