Asset Impairments, Restructuring, and Other Special Charges (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Unusual or Infrequent Item [Line Items]
Severance:									$ 697.4	$ 126.7	$ 141.0
Asset impairment (gains from facility sales) and other special charges:									462.5	255.8	226.7
Asset impairment, restructuring, and other special charges	$ 1,003.2	$ 406.5	$ 50.0	$ 213.9	$ 147.6	$ 45.5	$ 58.0	$ 131.4	1,673.6	382.5	367.7
Human pharmaceutical products
Unusual or Infrequent Item [Line Items]
Severance:									601.0	85.9	81.5
Asset impairment (gains from facility sales) and other special charges:									81.7	(13.0)	24.6
Animal health products
Unusual or Infrequent Item [Line Items]
Severance:									96.4	40.8	59.5
Asset impairment (gains from facility sales) and other special charges:									380.8	268.8	202.1
United States
Unusual or Infrequent Item [Line Items]
Total pension and post-retirement medical charges associated with U.S. early retirement program									513.7	0.0	0.0
United States | Human pharmaceutical products
Unusual or Infrequent Item [Line Items]
Total pension and post-retirement medical charges associated with U.S. early retirement program									446.7	0.0	0.0
United States | Animal health products
Unusual or Infrequent Item [Line Items]
Total pension and post-retirement medical charges associated with U.S. early retirement program									$ 67.0	$ 0.0	$ 0.0