Fair Value Measurement (Financial Assets and Liabilities Not Measured on a Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capital lease obligation	$ 349.5
Carrying amount | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capital lease obligation	349.5	$ 349.2
Fair value | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Capital lease obligation	349.5	349.2
Baxalta notes | Carrying amount | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	5,041.9	5,057.7
Baxalta notes | Fair value | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	5,085.9	5,229.9
SAIIDAC notes | Carrying amount | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	12,053.3	12,050.2
SAIIDAC notes | Fair value | Nonrecurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	$ 11,620.0	$ 11,913.7