Earnings (Loss) Per Share (Details)							12 Months Ended
	Aug. 01, 2020 shares	Jan. 23, 2020 shares	Jan. 22, 2020 shares	Jul. 18, 2019 shares	Sep. 24, 2018 shares	Sep. 19, 2018	Dec. 31, 2020 shares	Dec. 31, 2019 shares	Sep. 18, 2018 shares
Subsidiary, Sale of Stock [Line Items]
Stock split ratio						2,932,900
Number of shares issued (in shares)		25,000,000.0
Weighted average number diluted shares outstanding adjustment (in shares)								1,300,000
Antidilutive shares not included in calculation diluted earnings per share (in shares)								100,000
Bayer Animal Business
Subsidiary, Sale of Stock [Line Items]
Number of shares issued to previous shareholders upon closing (in shares)	72,900,000						72,900,000
Aratana Therapeutics, Inc.
Subsidiary, Sale of Stock [Line Items]
Number of shares issued to previous shareholders upon closing (in shares)				7,200,000				7,300,000
IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)					72,300,000
Common Stock Offering
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)			22,700,000
Weighted average number of shares issued basic (in shares)							25,000,000.0
Tangible Equity Unit
Subsidiary, Sale of Stock [Line Items]
Weighted average number of shares issued basic (in shares)							14,300,000
Elanco | Lilly
Subsidiary, Sale of Stock [Line Items]
Common shares outstanding (in shares)								293,300,000	100