Revenue Recognition - Disaggregation of Revenue By Major Product Category (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 72.6	$ 97.7	$ 206.0	$ 310.0
Lithium Hydroxide
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	43.9	52.9	115.4	178.2
Butyllithium
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	19.6	25.6	62.4	77.2
High Purity Lithium Metal and Other Specialty Compounds
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	7.1	11.7	23.0	38.8
Lithium Carbonate and Lithium Chloride
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 2.0	$ 7.5	$ 5.2	$ 15.8