Revenue (Disaggregation of Revenue by Product) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 5,859.8	$ 5,092.2
U.S.
Disaggregation of Revenue [Line Items]
Revenue	3,328.8	2,890.8
Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	2,531.0	2,201.4
Endocrinology
Disaggregation of Revenue [Line Items]
Revenue	2,968.9	2,553.0
Endocrinology | U.S.
Disaggregation of Revenue [Line Items]
Revenue	1,991.2	1,719.4
Endocrinology | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	977.7	833.6
Trulicity®
Disaggregation of Revenue [Line Items]
Revenue	1,229.4	879.7
Trulicity® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	929.5	665.6
Trulicity® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	299.9	214.1
Humalog®
Disaggregation of Revenue [Line Items]
Revenue	695.8	730.8
Humalog® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	398.6	448.6
Humalog® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	297.2	282.2
Humulin®
Disaggregation of Revenue [Line Items]
Revenue	315.7	297.7
Humulin® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	214.1	201.3
Humulin® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	101.5	96.4
Basaglar®
Disaggregation of Revenue [Line Items]
Revenue	303.7	251.4
Basaglar® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	230.4	198.2
Basaglar® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	73.3	53.2
Jardiance
Disaggregation of Revenue [Line Items]
Revenue	267.5	203.6
Jardiance | U.S.
Disaggregation of Revenue [Line Items]
Revenue	144.6	125.2
Jardiance | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	122.9	78.4
Trajenta
Disaggregation of Revenue [Line Items]
Revenue	93.2	131.9
Trajenta | U.S.
Disaggregation of Revenue [Line Items]
Revenue	28.7	47.4
Trajenta | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	64.5	84.6
Other Endocrinology
Disaggregation of Revenue [Line Items]
Revenue	63.6	57.9
Other Endocrinology | U.S.
Disaggregation of Revenue [Line Items]
Revenue	45.3	33.1
Other Endocrinology | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	18.4	24.7
Oncology
Disaggregation of Revenue [Line Items]
Revenue	1,201.5	1,012.7
Oncology | U.S.
Disaggregation of Revenue [Line Items]
Revenue	657.9	593.9
Oncology | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	543.6	418.9
Alimta®
Disaggregation of Revenue [Line Items]
Revenue	560.1	499.2
Alimta® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	324.2	281.8
Alimta® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	235.8	217.4
Cyramza®
Disaggregation of Revenue [Line Items]
Revenue	239.0	198.3
Cyramza® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	89.1	75.1
Cyramza® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	149.9	123.2
Verzenio®
Disaggregation of Revenue [Line Items]
Revenue	188.0	109.4
Verzenio® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	129.4	93.5
Verzenio® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	58.6	15.9
Erbitux®
Disaggregation of Revenue [Line Items]
Revenue	130.8	118.4
Erbitux® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	117.8	113.3
Erbitux® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	13.0	5.1
Other Oncology
Disaggregation of Revenue [Line Items]
Revenue	83.6	87.4
Other Oncology | U.S.
Disaggregation of Revenue [Line Items]
Revenue	(2.6)	30.2
Other Oncology | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	86.3	57.3
Immunology
Disaggregation of Revenue [Line Items]
Revenue	585.8	334.7
Immunology | U.S.
Disaggregation of Revenue [Line Items]
Revenue	341.4	187.2
Immunology | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	244.4	147.4
Taltz®
Disaggregation of Revenue [Line Items]
Revenue	443.5	252.5
Taltz® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	327.5	180.8
Taltz® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	116.0	71.7
Olumiant®
Disaggregation of Revenue [Line Items]
Revenue	139.7	82.1
Olumiant® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	11.3	6.4
Olumiant® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	128.4	75.7
Other Immunology
Disaggregation of Revenue [Line Items]
Revenue	2.6	0.0
Other Immunology | U.S.
Disaggregation of Revenue [Line Items]
Revenue	2.6	0.0
Other Immunology | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	0.0	0.0
Neuroscience
Disaggregation of Revenue [Line Items]
Revenue	463.5	393.1
Neuroscience | U.S.
Disaggregation of Revenue [Line Items]
Revenue	110.3	51.1
Neuroscience | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	353.2	342.0
Cymbalta®
Disaggregation of Revenue [Line Items]
Revenue	210.4	164.1
Cymbalta® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	11.6	10.3
Cymbalta® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	198.8	153.8
Zyprexa®
Disaggregation of Revenue [Line Items]
Revenue	98.4	107.2
Zyprexa® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	11.2	9.3
Zyprexa® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	87.2	97.9
Emgality®
Disaggregation of Revenue [Line Items]
Revenue	74.0	14.2
Emgality® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	67.3	12.2
Emgality® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	6.7	2.1
Other Neuroscience
Disaggregation of Revenue [Line Items]
Revenue	80.7	107.6
Other Neuroscience | U.S.
Disaggregation of Revenue [Line Items]
Revenue	20.2	19.3
Other Neuroscience | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	60.5	88.2
Other
Disaggregation of Revenue [Line Items]
Revenue	640.1	798.7
Other | U.S.
Disaggregation of Revenue [Line Items]
Revenue	228.0	339.2
Other | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	412.1	459.5
Forteo®
Disaggregation of Revenue [Line Items]
Revenue	272.4	312.9
Forteo® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	122.5	125.9
Forteo® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	149.8	187.0
Cialis®
Disaggregation of Revenue [Line Items]
Revenue	193.0	308.2
Cialis® | U.S.
Disaggregation of Revenue [Line Items]
Revenue	26.1	143.2
Cialis® | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	167.0	164.9
Other
Disaggregation of Revenue [Line Items]
Revenue	174.7	177.6
Other | U.S.
Disaggregation of Revenue [Line Items]
Revenue	79.4	70.1
Other | Outside U.S.
Disaggregation of Revenue [Line Items]
Revenue	$ 95.3	$ 107.6