LICENSING ARRANGEMENTS (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments for licensing and alliance arrangements	$ 41	$ 15	$ 619
Halozyme [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments for licensing and alliance arrangements	$ 105
Number of Collaboration Targets	11
Collaborative Arrangement Contingent Payments Maximum Exposure	$ 160
CytomX [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments for licensing and alliance arrangements	$ 75
Number of Collaboration Targets	8
Collaborative Arrangement Contingent Payments Maximum Exposure	$ 448
Number of Initial Collaboration Targets	4
Payment for Additional Targets Made To Collaborative Partner	$ 200
Biogen [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from out-licensed arrangements	300
Potential Milestone Receipts	410
Roche [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from out-licensed arrangements	170
Potential Milestone Receipts	$ 205