Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair value of assets and liabilities measured on a recurring basis
Total assets	$ 314,732	$ 311,302
Total liabilities	147,995	222,559
Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	145,974	214,895
Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	2,021	7,664
Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	9,951	73,676
Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	245,857	200,677
U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	12,364
Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	40,560	34,449
Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	6,000
Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total assets		2,500
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair value of assets and liabilities measured on a recurring basis
Total assets	9,951	73,676
Total liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	9,951	73,676
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total assets		0
Significant Other Observable Inputs (Level 2)
Fair value of assets and liabilities measured on a recurring basis
Total assets	304,781	237,626
Total liabilities	0	0
Significant Other Observable Inputs (Level 2) | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Significant Other Observable Inputs (Level 2) | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	0	0
Significant Other Observable Inputs (Level 2) | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Significant Other Observable Inputs (Level 2) | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	245,857	200,677
Significant Other Observable Inputs (Level 2) | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	12,364
Significant Other Observable Inputs (Level 2) | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	40,560	34,449
Significant Other Observable Inputs (Level 2) | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	6,000
Significant Other Observable Inputs (Level 2) | Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total assets		2,500
Significant Unobservable Inputs (Level 3)
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Total liabilities	147,995	222,559
Significant Unobservable Inputs (Level 3) | Contingent consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	145,974	214,895
Significant Unobservable Inputs (Level 3) | Contingent consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total liabilities	2,021	7,664
Significant Unobservable Inputs (Level 3) | Cash equivalents
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Significant Unobservable Inputs (Level 3) | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total assets	0
Significant Unobservable Inputs (Level 3) | Commercial paper
Fair value of assets and liabilities measured on a recurring basis
Total assets	0	0
Significant Unobservable Inputs (Level 3) | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total assets	$ 0
Significant Unobservable Inputs (Level 3) | Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total assets		$ 0