Acquisitions (Purchase Price Allocation) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Jan. 03, 2017	Dec. 31, 2016	Jan. 01, 2015
Business Acquisition [Line Items]
Goodwill	$ 4,370.1		$ 3,972.7
Boehringer
Business Acquisition [Line Items]
Inventories		$ 108.6
Marketed products		297.0
Property and equipment		148.2
Other assets and liabilities - net		8.2
Total identifiable net assets		562.0
Goodwill		320.1
Total consideration transferred - net of cash acquired		$ 882.1
Novartis Animal Health
Business Acquisition [Line Items]
Inventories				$ 380.2
Acquired in-process research and development				298.0
Marketed products				1,953.0
Property and equipment				199.9
Assets held for sale (primarily the U.S. Sentinel rights)				422.7
Accrued retirement benefits				(108.7)
Deferred income taxes				(60.1)
Other assets and liabilities - net				(73.0)
Total identifiable net assets				3,012.0
Goodwill				2,271.1
Total consideration transferred - net of cash acquired				$ 5,283.1