Segment Reporting Segment Information (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended
	Sep. 30, 2019		Mar. 31, 2019	Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018		Jun. 01, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net Sales	$ 1,911		$ 3,396	$ 1,947		$ 10,863		$ 11,472
Segment operating EBITDA	(176)			(213)	[1]	1,855	[1]	2,131	[1]
Segment Assets	39,352			39,388		39,352		39,388			$ 38,632
Goodwill	10,168			10,203		10,168		10,203		$ 10,179	10,193
Seed [Member]
Segment Reporting Information [Line Items]
Net Sales	681			551		6,347		6,716
Segment operating EBITDA	(295)			(372)		1,066		1,226
Segment Assets	26,021	[2],[3]		30,300	[2]	26,021	[2],[3]	30,300	[2]		29,286
Goodwill	5,447					5,447				5,453	0
Crop Protection [Member]
Segment Reporting Information [Line Items]
Net Sales	1,230			1,396		4,516		4,756
Segment operating EBITDA	119			159		789		905
Segment Assets	13,331	[2],[3]		$ 9,088	[2]	13,331	[2],[3]	$ 9,088	[2]		9,346
Goodwill	$ 4,721					$ 4,721				4,726	$ 0
Reallocation of goodwill [Member]
Segment Reporting Information [Line Items]
Goodwill										$ 3,382

[1] Periods prior to March 31, 2019 are on a pro forma basis, prepared in accordance with Article 11 of Regulation S-X.

[2] Segment assets at December 31, 2018 were $29,286 million and $9,346 million for Seed and Crop Protection, respectively.

[3] On June 1, 2019, as a result of changes in reportable segments, $3,382 million of goodwill was reallocated from the Seed reportable segment to the Crop Protection reportable segment.  This change was not reflected in segment assets prior to June 1, 2019.