Consolidated and Combined Statements of Equity - USD ($) shares in Millions, $ in Millions		Total	Aratana Therapeutics, Inc.	Common Stock	Common Stock Aratana Therapeutics, Inc.		Additional Paid-in Capital	Additional Paid-in Capital Aratana Therapeutics, Inc.	Net Parent Company Investment	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Foreign Currency Translation	Defined Benefit Pension and Retiree Health Benefit Plans
Balance at beginning of period (in shares) at Dec. 31, 2016				293.3
Balance at beginning of period at Dec. 31, 2016		$ 7,017.4		$ 0.0			$ 0.0		$ 7,474.3	$ 0.0	$ (456.9)	$ (437.3)	$ (19.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		(310.7)							(310.7)
Other comprehensive income (loss), net of tax		200.3									200.3	210.1	(9.8)
Transfers (to)/from Lilly, net		873.3							873.3
Balance at end of period (in shares) at Dec. 31, 2017				293.3
Balance at end of period at Dec. 31, 2017		7,780.3		$ 0.0			0.0		8,036.9	0.0	(256.6)	(227.2)	(29.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		86.5							70.1	16.4
Other comprehensive income (loss), net of tax		(21.7)									(21.7)	(47.1)	25.4
Transfers (to)/from Lilly, net		(226.3)							(226.3)
Separation adjustments	[1]	99.6							43.5		56.1	56.1
Issuance of common stock (in shares)				72.3
Issuance of common stock		1,659.7					1,659.7
Consideration to Lilly in connection with Separation		(4,194.9)					(4,194.9)
Reclassification of net parent company investment		0.0					7,923.9		(7,923.9)
Stock compensation		1.8					1.8
Capital contribution from Lilly		12.8					12.8
Balance at end of period (in shares) at Dec. 31, 2018				365.6
Balance at end of period at Dec. 31, 2018		5,197.5		$ 0.0			5,403.3		0.0	16.4	(222.2)	(218.2)	(4.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		67.9								67.9
Other comprehensive income (loss), net of tax		48.5									48.5	19.8	28.7
Separation adjustments	[2]	(51.2)					(51.2)
Stock compensation		40.7					40.7
Issuance of stock under employee stock plans, net (in shares)				0.1
Issuance to Aratana shareholders for acquisition (in shares)	[3]				7.2
Issuance to Aratana shareholders for acquisition	[3]		$ 238.0					$ 238.0
Accelerated vesting of equity awards (in shares)			0.1		0.1	[3]
Accelerated vesting of equity awards	[3]		$ 3.6					3.6
Other	[3]		1.9					$ 1.9
Balance at end of period (in shares) at Dec. 31, 2019				373.0
Balance at end of period at Dec. 31, 2019		$ 5,546.9	$ 5,546.9	$ 0.0			$ 5,636.3		$ 0.0	$ 84.3	$ (173.7)	$ (198.4)	$ 24.7

[1] See Note 3: Impact of Separation for further discussion.

[2] See Note 20: Related Party Agreements and Transactions for further discussion.

[3] See Note 6: Acquisitions for further discussion.