Revenue (Disaggregation of Revenue by Product) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 6,114.0	$ 5,476.6	$ 5,636.7	$ 5,092.2	$ 5,637.6	$ 5,306.9	$ 5,585.0	$ 4,963.8	$ 22,319.5	$ 21,493.3	$ 19,973.8
U.S.
Disaggregation of Revenue [Line Items]
Revenue									12,722.6	12,391.9	11,414.4
Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									9,596.8	9,101.4	8,559.4
Endocrinology | U.S.
Disaggregation of Revenue [Line Items]
Revenue									8,310.7	7,511.6	6,373.0
Endocrinology | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									4,503.7	4,190.5	3,712.2
Trulicity® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									3,155.2	2,515.8	1,609.8
Trulicity® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									972.7	683.3	419.9
Humalog® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									1,669.7	1,787.8	1,717.8
Humalog® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									1,151.0	1,208.7	1,147.4
Forteo® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									645.5	757.9	965.2
Forteo® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									759.1	817.7	783.8
Humulin® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									879.7	910.2	884.6
Humulin® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									410.4	421.2	450.7
Basaglar®
Disaggregation of Revenue [Line Items]
Revenue									1,112.6	801.2	432.1
Basaglar® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									876.2	622.8	311.1
Basaglar® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									236.3	178.5	121.0
Jardiance®
Disaggregation of Revenue [Line Items]
Revenue									944.2	658.3	447.5
Jardiance® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									565.9	400.2	290.4
Jardiance® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									378.3	258.1	157.0
Trajenta®
Disaggregation of Revenue [Line Items]
Revenue									590.6	574.7	537.9
Trajenta® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									224.8	224.2	213.2
Trajenta® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									365.8	350.5	324.7
Other Endocrinology | U.S.
Disaggregation of Revenue [Line Items]
Revenue									293.7	292.7	380.9
Other Endocrinology | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									230.1	272.5	307.7
Oncology | U.S.
Disaggregation of Revenue [Line Items]
Revenue									2,608.5	2,403.2	2,050.4
Oncology | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									2,005.9	1,857.3	1,761.6
Alimta® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									1,219.5	1,131.0	1,034.3
Alimta® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									896.4	1,001.9	1,028.2
Cyramza® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									335.3	291.5	278.8
Cyramza® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									589.9	529.9	479.6
Verzenio® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									454.8	248.5	21.0
Verzenio® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									124.9	6.6	0.0
Erbitux® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									487.9	531.6	541.7
Erbitux® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									55.4	103.8	104.2
Other Oncology | U.S.
Disaggregation of Revenue [Line Items]
Revenue									111.0	200.6	174.6
Other Oncology | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									339.3	215.1	149.6
Immunology | U.S.
Disaggregation of Revenue [Line Items]
Revenue									1,059.0	745.4	486.0
Immunology | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									734.3	394.6	119.0
Taltz® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									1,016.8	738.7	486.0
Taltz® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									349.6	198.7	73.2
Olumiant®
Disaggregation of Revenue [Line Items]
Revenue									426.9	202.5	45.8
Olumiant® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									42.2	6.7	0.0
Olumiant® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									384.7	195.9	45.8
Neuroscience | U.S.
Disaggregation of Revenue [Line Items]
Revenue									356.5	277.4	591.0
Neuroscience | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									1,366.4	1,543.3	1,580.1
Cymbalta® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									49.6	54.3	114.9
Cymbalta® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									675.8	653.7	642.2
Zyprexa® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									41.0	36.2	75.5
Zyprexa® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									377.6	435.1	505.7
Strattera® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									30.8	89.7	284.9
Strattera® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									211.7	361.1	333.3
Emgality® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									154.9	4.9	0.0
Emgality® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									7.7	0.0	0.0
Other Neuroscience | U.S.
Disaggregation of Revenue [Line Items]
Revenue									80.2	92.3	115.7
Other Neuroscience | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									93.6	93.4	98.9
Other | U.S.
Disaggregation of Revenue [Line Items]
Revenue									387.9	1,454.3	1,914.0
Other | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									986.5	1,115.7	1,386.5
Cialis ® | U.S.
Disaggregation of Revenue [Line Items]
Revenue									231.7	1,129.2	1,358.6
Cialis ® | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									658.8	722.7	964.5
Other | U.S.
Disaggregation of Revenue [Line Items]
Revenue									156.2	325.1	555.4
Other | Other foreign countries
Disaggregation of Revenue [Line Items]
Revenue									$ 327.7	$ 393.0	$ 422.0