Net Loss Per Common Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Total common stock equivalents (in shares)	5,368,320	4,270,882	4,927,251	3,940,304
Shares of common stock subject to outstanding options
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Total common stock equivalents (in shares)	5,320,885	4,270,882	4,890,309	3,940,304
Employee stock purchase plan
Outstanding shares of common stock equivalents that have been excluded from diluted net loss per common share
Total common stock equivalents (in shares)	47,435	0	36,942	0