XML 37 R25.htm IDEA: XBRL DOCUMENT v3.19.1
Cash, Cash Equivalents and Marketable Securities (Details) - USD ($)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Cash, Cash Equivalents and Marketable Securities    
Total cash, cash equivalents and marketable securities, Unrealized gains $ 189 $ 14
Total cash, cash equivalents and marketable securities, Unrealized losses (11) (333)
Carrying value    
Cash, Cash Equivalents and Marketable Securities    
Cash and cash equivalents 47,493 57,379
Total cash, cash equivalents and marketable securities, Cost 477,647 484,037
Fair value    
Cash, Cash Equivalents and Marketable Securities    
Cash and cash equivalents 47,493 57,379
Total cash, cash equivalents and marketable securities, Fair value $ 477,825 $ 483,718
Corporate debt securities due within 3 months of date of purchase    
Cash, Cash Equivalents and Marketable Securities    
Maturity period from date of purchase to classify an investment as marketable securities 3 months 3 months
Corporate debt securities due within 3 months of date of purchase | Carrying value | Level 2    
Cash, Cash Equivalents and Marketable Securities    
Marketable securities, cost   $ 11,974
Corporate debt securities due within 3 months of date of purchase | Fair value | Level 2    
Cash, Cash Equivalents and Marketable Securities    
Marketable securities, fair value   $ 11,974
Corporate debt securities due within 1 year of date of purchase    
Cash, Cash Equivalents and Marketable Securities    
Maturity period from date of purchase to classify an investment as marketable securities 1 year 1 year
Corporate debt securities due within 1 year of date of purchase | Level 2    
Cash, Cash Equivalents and Marketable Securities    
Marketable securities, unrealized gains $ 189 $ 14
Marketable securities, unrealized losses (11) (333)
Corporate debt securities due within 1 year of date of purchase | Carrying value | Level 2    
Cash, Cash Equivalents and Marketable Securities    
Marketable securities, cost 430,154 426,658
Corporate debt securities due within 1 year of date of purchase | Fair value | Level 2    
Cash, Cash Equivalents and Marketable Securities    
Marketable securities, fair value 430,332 426,339
Cash | Carrying value | Level 1    
Cash, Cash Equivalents and Marketable Securities    
Cash and cash equivalents 2,075 2,004
Cash | Fair value | Level 1    
Cash, Cash Equivalents and Marketable Securities    
Cash and cash equivalents 2,075 2,004
Money market funds | Carrying value | Level 1    
Cash, Cash Equivalents and Marketable Securities    
Cash and cash equivalents 45,418 43,401
Money market funds | Fair value | Level 1    
Cash, Cash Equivalents and Marketable Securities    
Cash and cash equivalents $ 45,418 $ 43,401