Earnings Per Share And Shareholder's Equity - Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended															12 Months Ended
		Dec. 31, 2020	[1]	Sep. 30, 2020	[2]	Jun. 30, 2020	[3]	Mar. 31, 2020	Dec. 31, 2019	[4]	Sep. 28, 2019	[5]	Jun. 29, 2019	[6]	Mar. 30, 2019	[7]	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income (loss)		$ (175.0)		$ (154.6)		$ 60.6		$ 106.4	$ (19.0)		$ 92.2		$ 9.0		$ 63.9		$ (162.6)	$ 146.1	$ 131.0
Denominator:
Basic (in shares)		135.4		136.5		136.4		136.2	136.1		136.0		136.0		135.9		136.1	136.0	137.8
Dilutive effect of share-based awards (in shares)	[8]																0.0	0.5	0.5
Diluted (in shares)		135.4		136.5		137.5		137.3	137.0		136.8		136.5		136.2		136.1	136.5	138.3
Antidilutive share-based awards outstanding (in shares)																	0.0	1.5	1.4

[1] Includes change in financial assets of $122.3 million and impairment charges of $144.4 million.

[2] Includes impairment charges of $202.4 million, change in financial assets of $22.2 million and loss on early debt extinguishment of $20.0 million.

[3] Includes Rosemont Pharmaceuticals business pre-tax loss of $21.1 million.

[4] Includes impairment charges of $141.6 million.

[5] Includes animal health divestiture pre-tax gain of $71.7 million, Ranitidine market withdrawal charges of $18.4 million, acquisition-related charges and contingent consideration adjustments of $18.1 million, and impairment charges of $10.9 million.

[6] Includes impairment charges of $27.8 million and restructuring charges and other termination benefits of $12.2 million.

[7] Includes change in financial assets of $10.4 million.

[8] In the period of a net loss, diluted shares equal basic shares