Fair Value Measurements - Assets and Liabilities at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Mar. 31, 2022
Assets:
Derivative contracts	$ 0.1
Other current liabilities:
Contingent consideration obligations	287.1	$ 0.0
Other non-current liabilities:
Contingent consideration obligations	$ 221.8
Samsung Bioepis
Other non-current liabilities:
Equity, ownership interest	49.90%		49.90%
Fair Value, Measurements Recurring
Assets:
Cash equivalents	$ 802.4	610.7
Marketable equity securities	304.7	416.8
Derivative contracts	6.0	11.9
Plan assets for deferred compensation	42.8	37.5
Total	1,156.0	1,506.9
Other current liabilities:
Derivative contracts	31.6
Contingent consideration obligations	287.1
Other non-current liabilities:
Derivative contracts	2.4
Contingent consideration obligations	221.8
Total	542.9	31.6
Derivative contracts		31.6
Total	542.9	31.6
Fair Value, Measurements Recurring | Samsung Bioepis
Assets:
Other current assets, receivable		430.0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements Recurring
Assets:
Cash equivalents	0.0	0.0
Marketable equity securities	304.7	416.8
Derivative contracts	0.0	0.0
Plan assets for deferred compensation	0.0	0.0
Derivative contracts	0.0
Total	304.7	416.8
Other current liabilities:
Derivative contracts	0.0
Contingent consideration obligations	0.0
Other non-current liabilities:
Derivative contracts	0.0
Contingent consideration obligations	0.0
Total	0.0	0.0
Derivative contracts		0.0
Total	0.0	0.0
Quoted Prices in Active Markets (Level 1) | Fair Value, Measurements Recurring | Samsung Bioepis
Assets:
Other current assets, receivable		0.0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements Recurring
Assets:
Cash equivalents	802.4	610.7
Marketable equity securities	0.0	0.0
Derivative contracts	6.0	11.9
Plan assets for deferred compensation	42.8	37.5
Derivative contracts	0.1
Total	851.3	660.1
Other current liabilities:
Derivative contracts	31.6
Contingent consideration obligations	0.0
Other non-current liabilities:
Derivative contracts	2.4
Contingent consideration obligations	0.0
Total	34.0	31.6
Derivative contracts		31.6
Total	34.0	31.6
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements Recurring | Samsung Bioepis
Assets:
Other current assets, receivable		0.0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements Recurring
Assets:
Cash equivalents	0.0	0.0
Marketable equity securities	0.0	0.0
Derivative contracts	0.0	0.0
Plan assets for deferred compensation	0.0	0.0
Derivative contracts	0.0
Total	0.0	430.0
Other current liabilities:
Derivative contracts	0.0
Contingent consideration obligations	287.1
Other non-current liabilities:
Derivative contracts	0.0
Contingent consideration obligations	221.8
Total	508.9	0.0
Derivative contracts		0.0
Total	$ 508.9	0.0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements Recurring | Samsung Bioepis
Assets:
Other current assets, receivable		$ 430.0