INVENTORIES AND PREPAID MANUFACTURING - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Inventory [Line Items]
Write-down of inventory			$ 1,061	$ 612
Benefit in cost of goods sold related to previously written down as excess inventory	$ 4,900		8,600
Auryxia Drug Substance
Inventory [Line Items]
Prepaid manufacturing costs	0		0		$ 500
Write-down of inventory	500	$ 300	1,100	$ 600
Vadadustat Drug Substance
Inventory [Line Items]
Prepaid manufacturing costs	$ 11,600		$ 11,600		$ 14,000