Planned Merger with Dow Chemical (Narrative) (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Proposed Merger with Dow Chemical [Line Items]
Timing of intended spinoffs after closing of merger, months	18		18
Merger related transaction costs	$ 216	$ 76	$ 386	$ 100
Scenario, Forecast [Member]
Proposed Merger with Dow Chemical [Line Items]
Payments to Acquire Businesses, Gross						$ 1,200
Business Combination, working capital						$ 425
Substantial Detriment					$ 350