Calico (Narrative) (Details) $ in Millions	39 Months Ended
	Dec. 31, 2016 USD ($)
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Payments to acquire interest in joint venture	$ 240
Commitment to Invest
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research commitments	490
Research and Development Arrangement | AbbVie Inc
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Accumulated payments for other commitments	750
Research and Development Arrangement | Calico
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research commitments	500
Accumulated payments for other commitments	$ 250