Net loss per share - Schedule of antidilutive securities excluded from computation of earnings per share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	19,537	15,840	19,864	12,146
Shares of common stock subject to outstanding options
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	3,365	3,647	3,419	3,691
Shares of common stock subject to outstanding warrants
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	330	586	396	596
Shares of common stock subject to outstanding RSUs
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	5,800	5,915	5,589	4,878
Shares of common stock subject to outstanding PRSUs
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	1,531	2,722	1,945	994
Shares of common stock pursuant to ESPP
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	312	229	316	219
Shares of common stock underlying Series A convertible preferred stock
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	125	125	125	896
Shares of common stock subject to convertible senior notes exercise
Antidilutive shares excluded from diluted net loss per share
Total shares of common stock equivalents (in shares)	8,074	2,616	8,074	872