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Cash Equivalents and Marketable Securities - Additional Information (Details) - US government and agency securities
$ in Millions
Mar. 31, 2016
Securitie
Dec. 31, 2015
USD ($)
Securitie
Cash Equivalents And Marketable Securities [Line Items]    
Number of securities in an unrealized loss position for less than one year 0 5
Fair value of debt securities in an unrealized loss position | $   $ 2.5
Number of securities in a significant unrealized loss position   0