Certain Transactions - Other Transactions - Additional Information (Detail) $ in Millions			1 Months Ended			3 Months Ended			6 Months Ended
	Jan. 08, 2018 USD ($)	May 12, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($) Lawsuit	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Jun. 30, 2017 USD ($)	Oct. 31, 2016 USD ($)
Noncash or Part Noncash Acquisitions [Line Items]
Other asset impairments, restructuring and other items						$ 1		$ 501
Net (gain) loss from sale of long-lived assets and investments						$ 2		106
PGT Healthcare Partnership [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Other asset impairments, restructuring and other items								64
Write-down of investment								94
Net (gain) loss from sale of long-lived assets and investments			$ 50
Rimsa [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Number of lawsuits filed \| Lawsuit					2
Alder [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment	$ 25
Collaborative agreement milestone payments	$ 175
Otsuka [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment		$ 50
Attenukine [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment				$ 30
Additional considerations				$ 280
Celltrion [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Refundable payment										$ 60
Total associated cost										$ 160
Regeneron [Member]
Noncash or Part Noncash Acquisitions [Line Items]
Upfront payment					$ 250
Collaborative agreement milestone payments							$ 25	$ 35	$ 60
Research and development costs					$ 1,000