Quarterly report pursuant to Section 13 or 15(d)

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

v3.4.0.3
Fair Value - Schedule of fair value of financial assets and liabilities inputs (Details) - USD ($)
$ in Thousands
Mar. 31, 2016
Dec. 31, 2015
Assets:    
Total assets measured at fair value $ 273,210 $ 312,519
Money market funds    
Assets:    
Total assets measured at fair value 112,561 180,021
Commercial paper    
Assets:    
Total assets measured at fair value 77,342 35,881
Corporate debt securities    
Assets:    
Total assets measured at fair value 81,306 79,421
U.S. government and government agency debt securities    
Assets:    
Total assets measured at fair value 2,001 17,196
Quoted Prices in Active Markets for Identical Instruments (Level 1)    
Assets:    
Total assets measured at fair value 112,561 180,021
Quoted Prices in Active Markets for Identical Instruments (Level 1) | Money market funds    
Assets:    
Total assets measured at fair value 112,561 180,021
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 0
Significant Other Observable Inputs (Level 2)    
Assets:    
Total assets measured at fair value 160,649 132,498
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 77,342 35,881
Significant Other Observable Inputs (Level 2) | Corporate debt securities    
Assets:    
Total assets measured at fair value 81,306 79,421
Significant Other Observable Inputs (Level 2) | U.S. government and government agency debt securities    
Assets:    
Total assets measured at fair value $ 2,001 $ 17,196