Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2020

Earnings Per Share [Abstract]

Basic and diluted net loss per share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Numerator:
Net loss attributable to common stockholders ($ in millions)	$	(21.0)	$	(23.1)	$	(57.5)	$	(44.7)
Denominator:
Weighted average common shares outstanding — basic and diluted	11,891,979		11,072,985		11,750,198		11,028,667
Net loss per share attributable to common stockholders — basic and diluted	$	(1.77)	$	(2.09)	$	(4.89)	$	(4.05)

Antidilutive potential common shares

The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:

	As of June 30,
	2020	2019
Options to purchase common stock	4,578,520	2,102,124
Convertible preferred stock (as converted to common stock)	31,557,107	28,595,471
	36,135,627	30,697,595