Fair Value Measurements - Fair Value Hierarchy (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair value of assets and liabilities measured on a recurring basis
Total Assets	$ 310,668	$ 102,144
Total Liabilities	222,945	218,702
Transfers or reclassifications of securities from Level 1 to Level 2	0
Transfers or reclassifications of securities from Level 2 to Level 1	0
Acquisition Related Contingent Consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	8,660	12,102
Acquisition Related Contingent Consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	214,285	206,600
Money market funds
Fair value of assets and liabilities measured on a recurring basis
Total Assets	35,325	77,254
Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	173,606	24,890
Commercial paper.
Fair value of assets and liabilities measured on a recurring basis
Total Assets	7,490
Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total Assets	10,001
Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	84,246
Fair Value, Inputs, Level 1
Fair value of assets and liabilities measured on a recurring basis
Total Assets	35,325	77,254
Fair Value, Inputs, Level 1 | Money market funds
Fair value of assets and liabilities measured on a recurring basis
Total Assets	35,325	77,254
Fair Value, Inputs, Level 2
Fair value of assets and liabilities measured on a recurring basis
Total Assets	275,343	24,890
Fair Value, Inputs, Level 2 | Corporate debt securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	173,606	24,890
Fair Value, Inputs, Level 2 | Commercial paper.
Fair value of assets and liabilities measured on a recurring basis
Total Assets	7,490
Fair Value, Inputs, Level 2 | Certificates of deposit
Fair value of assets and liabilities measured on a recurring basis
Total Assets	10,001
Fair Value, Inputs, Level 2 | Municipal securities
Fair value of assets and liabilities measured on a recurring basis
Total Assets	84,246
Fair Value, Inputs, Level 3
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	222,945	218,702
Fair Value, Inputs, Level 3 | Acquisition Related Contingent Consideration | MuGard
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	8,660	12,102
Fair Value, Inputs, Level 3 | Acquisition Related Contingent Consideration | Lumara Health
Fair value of assets and liabilities measured on a recurring basis
Total Liabilities	$ 214,285	$ 206,600