Revenue Recognition - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended	45 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Prior period performance obligation revenue recognized			$ 23,400,000	$ 30,700,000
Overpayments received period		10 years
Overpayment reimbursement liability	$ 32,500,000		32,500,000		$ 32,500,000	$ 32,500,000	$ 30,000,000
Revenue recognized					0
Total revenues	249,815,000	$ 246,040,000	768,412,000	805,022,000
Contract liability	89,800,000		89,800,000		89,800,000	89,800,000	$ 140,400,000
Rayaldee
Disaggregation of Revenue [Line Items]
Revenue recognized	5,800,000		14,300,000
Total revenues			24,074,000
Transfer of intellectual property and other
Disaggregation of Revenue [Line Items]
Total revenues	21,609,000	22,369,000	56,463,000	67,697,000
Pfizer | Collaborative Arrangement, Product
Disaggregation of Revenue [Line Items]
Revenue recognized						0
Contract liability	81,200,000		81,200,000		$ 81,200,000	$ 81,200,000
Pfizer | Collaborative Arrangement, Product | Transfer of intellectual property and other
Disaggregation of Revenue [Line Items]
Total revenues	$ 18,900,000	$ 21,800,000	$ 49,900,000	$ 54,200,000