Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue from products	$ 27,851	$ 22,231
Revenue from transfer of intellectual property and other	15,748	15,606	$ 15,606
Contract liability	125,000		$ 140,400
Rayaldee
Disaggregation of Revenue [Line Items]
Revenue from products	3,700
Pfizer | Collaborative Arrangement, Product
Disaggregation of Revenue [Line Items]
Revenue from transfer of intellectual property and other	14,700	$ 14,100
Contract liability	$ 116,400