Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Fair value, measurements, recurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets:
Cash equivalents	$ 4,591	$ 9,951
Total Assets	141,184	314,732
Liabilities:
Total Liabilities	50,085	147,995
Lumara Health Inc.
Liabilities:
Contingent Consideration	49,187	145,974
MuGard
Liabilities:
Contingent Consideration	898	2,021
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	4,591	9,951
Total Assets	4,591	9,951
Liabilities:
Total Liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Lumara Health Inc.
Liabilities:
Contingent Consideration	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | MuGard
Liabilities:
Contingent Consideration	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	0	0
Total Assets	136,593	304,781
Liabilities:
Total Liabilities	0	0
Significant Other Observable Inputs (Level 2) | Lumara Health Inc.
Liabilities:
Contingent Consideration	0	0
Significant Other Observable Inputs (Level 2) | MuGard
Liabilities:
Contingent Consideration	0	0
Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0	0
Total Assets	0	0
Liabilities:
Total Liabilities	50,085	147,995
Significant Unobservable Inputs (Level 3) | Lumara Health Inc.
Liabilities:
Contingent Consideration	49,187	145,974
Significant Unobservable Inputs (Level 3) | MuGard
Liabilities:
Contingent Consideration	898	2,021
Corporate debt securities
Assets:
Available-for-sale securities	116,152	245,857
Corporate debt securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available-for-sale securities	0	0
Corporate debt securities | Significant Other Observable Inputs (Level 2)
Assets:
Available-for-sale securities	116,152	245,857
Corporate debt securities | Significant Unobservable Inputs (Level 3)
Assets:
Available-for-sale securities	0	0
U.S. treasury and government agency securities
Assets:
Available-for-sale securities	9,291	12,364
U.S. treasury and government agency securities | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available-for-sale securities	0	0
U.S. treasury and government agency securities | Significant Other Observable Inputs (Level 2)
Assets:
Available-for-sale securities	9,291	12,364
U.S. treasury and government agency securities | Significant Unobservable Inputs (Level 3)
Assets:
Available-for-sale securities	0	0
Commercial paper
Assets:
Available-for-sale securities	1,999	40,560
Commercial paper | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available-for-sale securities	0	0
Commercial paper | Significant Other Observable Inputs (Level 2)
Assets:
Available-for-sale securities	1,999	40,560
Commercial paper | Significant Unobservable Inputs (Level 3)
Assets:
Available-for-sale securities	0	0
Certificates of deposit
Assets:
Available-for-sale securities	9,151	6,000
Certificates of deposit | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Available-for-sale securities	0	0
Certificates of deposit | Significant Other Observable Inputs (Level 2)
Assets:
Available-for-sale securities	9,151	6,000
Certificates of deposit | Significant Unobservable Inputs (Level 3)
Assets:
Available-for-sale securities	$ 0	$ 0