Quarterly report pursuant to Section 13 or 15(d)

Fair Value - Schedule of fair value of financial assets and liabilities inputs (Details)

v3.5.0.2
Fair Value - Schedule of fair value of financial assets and liabilities inputs (Details) - USD ($)
$ in Thousands
Jun. 30, 2016
Dec. 31, 2015
Assets:    
Total assets measured at fair value $ 243,564 $ 312,519
Money market funds    
Assets:    
Total assets measured at fair value 112,607 180,021
Commercial paper    
Assets:    
Total assets measured at fair value 51,682 35,881
Corporate debt securities    
Assets:    
Total assets measured at fair value 79,275 79,421
U.S. government and government agency debt securities    
Assets:    
Total assets measured at fair value   17,196
Quoted Prices in Active Markets for Identical Instruments (Level 1)    
Assets:    
Total assets measured at fair value 112,607 180,021
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Money market funds    
Assets:    
Total assets measured at fair value 112,607 180,021
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Commercial paper    
Assets:    
Total assets measured at fair value 0 0
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Corporate debt securities    
Assets:    
Total assets measured at fair value 0 0
Quoted Prices in Active Markets for Identical Instruments (Level 1) | U.S. government and government agency debt securities    
Assets:    
Total assets measured at fair value   0
Significant Other Observable Inputs (Level 2)    
Assets:    
Total assets measured at fair value 130,957 132,498
Significant Other Observable Inputs (Level 2) | Money market funds    
Assets:    
Total assets measured at fair value 0 0
Significant Other Observable Inputs (Level 2) | Commercial paper    
Assets:    
Total assets measured at fair value 51,682 35,881
Significant Other Observable Inputs (Level 2) | Corporate debt securities    
Assets:    
Total assets measured at fair value $ 79,275 79,421
Significant Other Observable Inputs (Level 2) | U.S. government and government agency debt securities    
Assets:    
Total assets measured at fair value   $ 17,196