XML 22 R25.htm IDEA: XBRL DOCUMENT v3.2.0.727
Fair value measurements - Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Jun. 30, 2015
Dec. 31, 2014
Assets:    
Assets, fair value disclosure, recurring $ 936,445 $ 492,003
Liabilities:    
Liabilities, fair value disclosure, recurring 7,984 6,796
Contingent consideration obligations [Member]    
Liabilities:    
Liabilities, fair value disclosure, recurring 7,984 6,796
Cash and Cash Equivalents [Member]    
Assets:    
Assets, fair value disclosure, recurring 593,299 347,845
U.S. Government Agency Securities [Member]    
Assets:    
Assets, fair value disclosure, recurring 329,299 131,536
Certificates of Deposit [Member]    
Assets:    
Assets, fair value disclosure, recurring 13,847 12,622
Quoted prices in active markets (Level 1) [Member]    
Assets:    
Assets, fair value disclosure, recurring 593,299 347,845
Quoted prices in active markets (Level 1) [Member] | Cash and Cash Equivalents [Member]    
Assets:    
Assets, fair value disclosure, recurring 593,299 347,845
Significant other observable inputs (Level 2) [Member]    
Assets:    
Assets, fair value disclosure, recurring 343,146 144,158
Significant other observable inputs (Level 2) [Member] | U.S. Government Agency Securities [Member]    
Assets:    
Assets, fair value disclosure, recurring 329,299 131,536
Significant other observable inputs (Level 2) [Member] | Certificates of Deposit [Member]    
Assets:    
Assets, fair value disclosure, recurring 13,847 12,622
Significant unobservable inputs (Level 3) [Member]    
Liabilities:    
Liabilities, fair value disclosure, recurring 7,984 6,796
Significant unobservable inputs (Level 3) [Member] | Contingent consideration obligations [Member]    
Liabilities:    
Liabilities, fair value disclosure, recurring $ 7,984 $ 6,796