Net loss per share (Tables)

3 Months Ended

Mar. 31, 2018

Net loss per share

Schedule of antidilutive securities excluded from the computation of earnings per share

	Three Months Ended
	March 31,
	2018	2017
Outstanding stock options and awards	13,104,711	12,598,407
Common shares issuable upon conversion of the 2018 Notes	148,836	505,004
Common shares issuable upon conversion of the 2020 Notes	368,939	407,000
Total potential common shares excluded from diluted net loss per share computation	13,622,486	13,510,411