Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Fair value of assets and liabilities measured on a recurring basis
Transfers or reclassifications of securities from Level 1 to Level 2	$ 0
Fair value, measurements, recurring
Fair value of assets and liabilities measured on a recurring basis
Total assets	140,617,000	$ 314,732,000
Total liabilities	150,663,000	147,995,000
Fair value, measurements, recurring | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	148,797,000	145,974,000
Fair value, measurements, recurring | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	1,866,000	2,021,000
Fair value, measurements, recurring | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	1,522,000	9,951,000
Fair value, measurements, recurring | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	93,103,000	245,857,000
Fair value, measurements, recurring | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	10,832,000	12,364,000
Fair value, measurements, recurring | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	16,708,000	40,560,000
Fair value, measurements, recurring | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	18,452,000	6,000,000
Fair value, measurements, recurring | (Level 1)
Fair value of assets and liabilities measured on a recurring basis
Total assets	1,522,000	9,951,000
Total liabilities	0	0
Fair value, measurements, recurring | (Level 1) | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Fair value, measurements, recurring | (Level 1) | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Fair value, measurements, recurring | (Level 1) | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	1,522,000	9,951,000
Fair value, measurements, recurring | (Level 1) | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 1) | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 1) | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 1) | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 2)
Fair value of assets and liabilities measured on a recurring basis
Total assets	139,095,000	304,781,000
Total liabilities	0	0
Fair value, measurements, recurring | (Level 2) | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Fair value, measurements, recurring | (Level 2) | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Fair value, measurements, recurring | (Level 2) | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 2) | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	93,103,000	245,857,000
Fair value, measurements, recurring | (Level 2) | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	10,832,000	12,364,000
Fair value, measurements, recurring | (Level 2) | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	16,708,000	40,560,000
Fair value, measurements, recurring | (Level 2) | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	18,452,000	6,000,000
Fair value, measurements, recurring | (Level 3)
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Total liabilities	150,663,000	147,995,000
Fair value, measurements, recurring | (Level 3) | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	148,797,000	145,974,000
Fair value, measurements, recurring | (Level 3) | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	1,866,000	2,021,000
Fair value, measurements, recurring | (Level 3) | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 3) | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 3) | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 3) | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Fair value, measurements, recurring | (Level 3) | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	$ 0	$ 0