Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Mar. 31, 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
Transfers or reclassifications of securities from Level 2 to Level 1	0
Fair Value, Measurements, Recurring
Fair value of assets and liabilities measured on a recurring basis
Total assets	315,473,000	$ 314,732,000
Total liabilities	148,955,000	147,995,000
Fair Value, Measurements, Recurring | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	146,973,000	145,974,000
Fair Value, Measurements, Recurring | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	1,982,000	2,021,000
Fair Value, Measurements, Recurring | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	9,932,000	9,951,000
Fair Value, Measurements, Recurring | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	248,374,000	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	16,840,000	12,364,000
Fair Value, Measurements, Recurring | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	26,875,000	40,560,000
Fair Value, Measurements, Recurring | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	13,452,000	6,000,000
Fair Value, Measurements, Recurring | Level 1
Fair value of assets and liabilities measured on a recurring basis
Total assets	9,932,000	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	9,932,000	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	305,541,000	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	248,374,000	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	16,840,000	12,364,000
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	26,875,000	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	13,452,000	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	148,955,000	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	146,973,000	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	1,982,000	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