Acquisitions and Divestitures - 2016 Acquisitions (Details) $ in Millions						6 Months Ended		9 Months Ended	12 Months Ended
	Dec. 20, 2017 product	Aug. 02, 2016 USD ($)	Mar. 01, 2016 USD ($)	Jan. 22, 2016 USD ($)	May 01, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 27, 2014 USD ($)	Oct. 01, 2016	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 27, 2015 USD ($)
Business Acquisition [Line Items]
Finite lived assets, useful life								20 years
Research and development						$ 88.2	$ 89.8		$ 167.7	$ 184.0	$ 187.8
Benzaclin
Business Acquisition [Line Items]
Effective date of acquisition		Aug. 02, 2016
Percentage of interest acquired		60.90%
Purchase price paid		$ 62.0
Benzaclin | Distribution and license agreements, supply agreements
Business Acquisition [Line Items]
Finite lived assets, useful life		9 years
Tretinoin Products
Business Acquisition [Line Items]
Effective date of acquisition				Jan. 22, 2016
Purchase price paid				$ 416.4
Contingent consideration				$ 0.0
Tretinoin Products | Developed product technology, formulations, and product rights
Business Acquisition [Line Items]
Finite lived assets, useful life				20 years
Tretinoin Products | Non-compete agreements
Business Acquisition [Line Items]
Finite lived assets, useful life				5 years
Development-Stage Rx Products
Business Acquisition [Line Items]
Purchase price paid			$ 0.0
Research and development					$ 18.0
Contingent consideration			$ 24.9
Number of products sold | product	1
Development-Stage Rx Products | Minimum
Business Acquisition [Line Items]
Royalty payment period			7 years
Development-Stage Rx Products | Maximum
Business Acquisition [Line Items]
Royalty payment period			10 years