Fair Value Measurements - Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair value of assets and liabilities measured on a recurring basis
Total Assets	$ 313,155	$ 311,302
Total Liabilities	227,550	222,559
Acquisition Related Contingent Consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	219,581	214,895
Acquisition Related Contingent Consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	7,969	7,664
Money market funds
Fair value of assets and liabilities measured on a recurring basis
Total Assets	36,339	73,676
Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	250,809	200,677
U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	4,528
Commercial paper.
Fair value of assets and liabilities measured on a recurring basis
Total Assets	18,977	34,449
Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	2,502	2,500
Fair Value, Inputs, Level 1
Fair value of assets and liabilities measured on a recurring basis
Total Assets	36,339	73,676
Fair Value, Inputs, Level 1 | Money market funds
Fair value of assets and liabilities measured on a recurring basis
Total Assets	36,339	73,676
Fair Value, Inputs, Level 2
Fair value of assets and liabilities measured on a recurring basis
Total Assets	276,816	237,626
Fair Value, Inputs, Level 2 | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	250,809	200,677
Fair Value, Inputs, Level 2 | U.S. treasury and government agency securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	4,528
Fair Value, Inputs, Level 2 | Commercial paper.
Fair value of assets and liabilities measured on a recurring basis
Total Assets	18,977	34,449
Fair Value, Inputs, Level 2 | Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	2,502	2,500
Fair Value, Inputs, Level 3
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	227,550	222,559
Fair Value, Inputs, Level 3 | Acquisition Related Contingent Consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	219,581	214,895
Fair Value, Inputs, Level 3 | Acquisition Related Contingent Consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	$ 7,969	$ 7,664