Stock-based compensation plan - Summary of SARs (Details) - SARs $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Number of SARs
Outstanding as of beginning of period (in shares) | shares	25,921,250
Granted (in shares) | shares	11,625,000
Exercised (in shares) | shares	(3,163,750)
Forfeited (in shares) | shares	(1,438,750)
Outstanding as of end of period (in shares) | shares	32,943,750
Vested and expected to vest (in shares) | shares	31,699,063
Vested (in shares) | shares	8,050,000
Weighted- Average Award Price in U.S. Cents*
Outstanding as of beginning of period (in dollars per share) | $ / shares	$ 0.20
Granted (in dollars per share) | $ / shares	0.47
Exercised (in dollars per share) | $ / shares	0.18
Forfeited (in dollars per share) | $ / shares	0.32
Outstanding as of end of period (in dollars per share) | $ / shares	0.29
Vested and expected to vest (in dollars per share) | $ / shares	0.29
Vested (in dollars per share) | $ / shares	$ 0.18
Weighted Average Remaining Contractual Term, Outstanding	3 years 6 months 18 days
Weighted Average Remaining Contractual Term, Vested and expected to vest	3 years 6 months 10 days
Weighted Average Remaining Contractual Term, Vested	2 years 2 months 4 days
Aggregate Intrinsic Value, Vested and expected to vest | $	$ 3,129
Aggregate Intrinsic Value, Vested | $	$ 1,301