Stock compensation - Shares available for grant (Details)	6 Months Ended
	Jun. 30, 2019 shares
Shares Available For Grant
Outstanding at the beginning of the period (in shares)	7,023,328
Additional authorization (in shares)	7,700,000
Options, RSUs and PSUs granted (in shares)	(2,891,106)
Options, RSUs and PSUs cancelled (in shares)	673,580
Outstanding at the end of the period (in shares)	12,505,802