Intangible Assets and Goodwill - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 329,675	$ 329,675
Accumulated Amortization	(10,622)	(1,522)
ASC 842 Adjustment	(540)
Total	318,513	328,153
Developed Product Rights for Auryxia
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	329,130	329,130
Accumulated Amortization	(10,617)	(1,517)
Total	$ 318,513	$ 327,613
Estimated useful life	9 years	9 years
Favourable Lease
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 545	$ 545
Accumulated Amortization	(5)	(5)
ASC 842 Adjustment	$ (540)
Total		$ 540
Estimated useful life		4 years