Note 13 - Revenue Recognition (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Contract with Customer, Performance Obligation Satisfied in Previous Period			$ 700	$ 900
Accrued Expense, Payor Overpayment Reimbursement, Liability	$ 2,600		2,600		$ 2,000
Revenue from Contract with Customer, Excluding Assessed Tax	156,807	$ 182,186	306,759	355,872
Contract Manufacturers [Member] | Milestone Payments [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,000		2,500
Contract Manufacturers [Member] | Milestone Payments [Member] | Minimum [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	300		400
Contract Manufacturers [Member] | Milestone Payments [Member] | Maximum [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,300		2,900
Rayaldee [Member]
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Revenue Recognized	7,200	7,200	13,500	14,100
Revenue from Contract with Customer, Excluding Assessed Tax	14,528	18,424	27,638	33,582
Intellectual Property and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	15,000	12,300	27,200	21,100
Increase (Decrease), Revenue from Contract with Customer, Excluding Assessed Tax	2,700		6,200
Intellectual Property and Other [Member] | Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | Development and License Agreement [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,500	5,000	13,500	7,200
Transfer of Intellectual Property and Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	14,963	12,306	27,229	21,054
Transfer of Intellectual Property and Other [Member] | Vifor Fresenius Medical Care Renal Pharma Ltd. [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,100	$ 6,300	10,600	$ 11,900
Offset amount	200		1,300
Transfer of Intellectual Property and Other [Member] | Vifor Fresenius Medical Care Renal Pharma Ltd. [Member] | Development and License Agreement [Member]
Disaggregation of Revenue [Line Items]
Increase (Decrease), Revenue from Contract with Customer, Excluding Assessed Tax	$ 1,500		$ 6,300