2017 DWDP Cost Synergy Program (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Nov. 01, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring, Settlement and Impairment Provisions		$ 139	$ 0	$ 126	$ 452
Employee Severance [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring, Settlement and Impairment Provisions		139
Payments for Restructuring		19
Restructuring Reserve		$ 120		$ 120
Subsequent Event [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						$ 1,300
Minimum [Member] | Subsequent Event [Member] | Employee Severance [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						525
Minimum [Member] | Subsequent Event [Member] | Impairment of Long-Lived Assets and Other Assets [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						400
Minimum [Member] | Subsequent Event [Member] | Costs Associated with Exit and Disposal Activities [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						290
Maximum [Member] | Subsequent Event [Member] | Employee Severance [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						575
Maximum [Member] | Subsequent Event [Member] | Impairment of Long-Lived Assets and Other Assets [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						440
Maximum [Member] | Subsequent Event [Member] | Costs Associated with Exit and Disposal Activities [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Cost						$ 310
Scenario, Forecast [Member] | 2017 DWDP Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring, Settlement and Impairment Provisions	$ 900