Segment Disclosures (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment reporting information
Net sales	$ 4,124	$ 4,590	$ 4,429
Ammonia
Segment reporting information
Net sales	1,020	1,113	1,028
Granular Urea
Segment reporting information
Net sales	1,248	1,342	1,322
UAN
Segment reporting information
Net sales	1,063	1,270	1,234
AN
Segment reporting information
Net sales	455	506	460
Operating segments | Ammonia
Segment reporting information
Net sales	1,020	1,113	1,028
Operating segments | Granular Urea
Segment reporting information
Net sales	1,248	1,342	1,322
Operating segments | UAN
Segment reporting information
Net sales	1,063	1,270	1,234
Operating segments | AN
Segment reporting information
Net sales	455	506	460
Operating segments | Other
Segment reporting information
Net sales	$ 338	$ 359	$ 385