Acquisitions and Divestitures - Narrative (Details) $ / shares in Units, shares in Millions, $ in Millions					3 Months Ended	6 Months Ended		12 Months Ended
	Aug. 31, 2020 USD ($) $ / shares	Jul. 27, 2020 USD ($)	Jul. 31, 2019 USD ($)	Jul. 18, 2019 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) shares	Mar. 31, 2020 numberOfDivestitures	Jan. 31, 2020 USD ($)
Business Acquisition [Line Items]
Number of divestitures | numberOfDivestitures									3
Forecast
Business Acquisition [Line Items]
Volume weighted average stock price as of the last day of trading before the closing of the acquisition duration	20 years
Volume weighted average price for thirty trading days (usd per share) | $ / shares	$ 33.60
Held for Sale | Worldwide rights to Osurnia and U.S. rights to Capstar
Business Acquisition [Line Items]
Cash received in agreement to divest										$ 285.0
Held for Sale | Worldwide Rights To Osurnia | Subsequent Event
Business Acquisition [Line Items]
Cash proceeds		$ 141.6
Aratana
Business Acquisition [Line Items]
Shares issued to previous shareholders upon closing (in shares) | shares				7.2
Value of shares issued as consideration				$ 238.0
Contingent value rights included in purchase consideration				$ 12.0
Contingent payment (usd per share) | $ / shares				$ 0.25
Measurement period adjustment					$ 19.1	$ 19.1
Accelerated vesting of equity awards (in shares) | shares								0.1
Accelerated stock based compensation expense								$ 3.6
Pro forma combined revenues							$ 1,520.6
Pro forma combined income before income taxes							$ 82.3
Galliprant
Business Acquisition [Line Items]
Contingent consideration liability				$ 84.7
Loss upon settlement of contingent consideration liability								$ 7.5
Prevtec
Business Acquisition [Line Items]
Contingent value rights included in purchase consideration			$ 16.3
Contingent consideration liability			4.7
Loss upon settlement of contingent consideration liability					$ 2.1
Consideration paid for acquisition			60.3
Settlement of accounts receivable			$ 0.7
Bayer Animal Business | Forecast
Business Acquisition [Line Items]
Value of shares issued as consideration	$ 2,300.0
Amount paid at closing	$ 5,300.0
Symmetrical collar (as a percent)	7.50%