Intangible Assets and Goodwill - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 214,148		$ 214,148	$ 329,675
Accumulated Amortization	(62,230)		(62,230)	(37,923)
ASC 842 Adjustment	(540)		(540)	(540)
Total	151,378		151,378	291,212
Developed product rights for Auryxia
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	213,603		213,603	329,130
Accumulated Amortization	(62,225)		(62,225)	(37,918)
Total	$ 151,378		$ 151,378	$ 291,212
Estimated useful life	7 years	9 years	7 years	9 years
Favorable lease
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 545		$ 545	$ 545
Accumulated Amortization	(5)		(5)	(5)
ASC 842 Adjustment	(540)		(540)	(540)
Total	$ 0		$ 0	$ 0