Net Income (Loss) Per Share - Schedule of EPS (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator
Net loss attributable to common stockholders	$ 32.7	$ (17.0)	$ 89.5	$ (46.1)
Denominator
Weighted-average number of common shares outstanding used in computing basic net income (loss) per share (in shares)	414.2	414.4	415.2	412.4
Net income (loss) per common share, basic (in dollars per share)	$ 0.08	$ (0.04)	$ 0.22	$ (0.11)
Numerator
Net income (loss)	$ 32.7	$ (17.0)	$ 89.5	$ (46.1)
Diluted net income (loss) per share:
Weighted-average number of common shares outstanding used in computing basic net income (loss) per share (in shares)	414.2	414.4	415.2	412.4
Weighted-average shares used in computed net income (loss) per share attributable to common shareholders, diluted (in shares)	419.9	414.4	419.9	412.4
Diluted net income (loss) per share (in dollars per share)	$ 0.08	$ (0.04)	$ 0.21	$ (0.11)
Class A
Numerator
Net loss attributable to common stockholders	$ 25.0	$ (10.4)	$ 61.7	$ (26.1)
Denominator
Weighted-average number of common shares outstanding used in computing basic net income (loss) per share (in shares)	316.3	252.7	286.1	233.1
Net income (loss) per common share, basic (in dollars per share)	$ 0.08	$ (0.04)	$ 0.22	$ (0.11)
Numerator
Net income (loss)	$ 25.0	$ (10.4)	$ 61.7	$ (26.1)
Reallocation of net income as a result of conversion of Class B to Class A common stock	7.7	0.0	27.8	0.0
Reallocation of net income to Class B common stock	0.0	0.0	0.0	0.0
Net income (loss) attributable to common stockholders for diluted EPS	$ 32.7	$ (10.4)	$ 89.5	$ (26.1)
Diluted net income (loss) per share:
Weighted-average number of common shares outstanding used in computing basic net income (loss) per share (in shares)	316.3	252.7	286.1	233.1
Weighted-average effect of dilutive RSUs and employee stock options (in shares)	5.5	0.0	4.4	0.0
Conversion of Class B to Class A common stock (in shares)	97.8	0.0	129.1	0.0
Weighted-average shares used in computed net income (loss) per share attributable to common shareholders, diluted (in shares)	419.7	252.7	419.6	233.1
Diluted net income (loss) per share (in dollars per share)	$ 0.08	$ (0.04)	$ 0.21	$ (0.11)
Class B
Numerator
Net loss attributable to common stockholders	$ 7.7	$ (6.6)	$ 27.8	$ (20.0)
Denominator
Weighted-average number of common shares outstanding used in computing basic net income (loss) per share (in shares)	97.8	161.7	129.1	179.3
Net income (loss) per common share, basic (in dollars per share)	$ 0.08	$ (0.04)	$ 0.22	$ (0.11)
Numerator
Net income (loss)	$ 7.7	$ (6.6)	$ 27.8	$ (20.0)
Reallocation of net income as a result of conversion of Class B to Class A common stock	0.0	0.0	0.0	0.0
Reallocation of net income to Class B common stock	(0.1)	0.0	(0.2)	0.0
Net income (loss) attributable to common stockholders for diluted EPS	$ 7.6	$ (6.6)	$ 27.6	$ (20.0)
Diluted net income (loss) per share:
Weighted-average number of common shares outstanding used in computing basic net income (loss) per share (in shares)	97.8	161.7	129.1	179.3
Weighted-average effect of dilutive RSUs and employee stock options (in shares)	0.2	0.0	0.3	0.0
Conversion of Class B to Class A common stock (in shares)	0.0	0.0	0.0	0.0
Weighted-average shares used in computed net income (loss) per share attributable to common shareholders, diluted (in shares)	98.0	161.7	129.4	179.3
Diluted net income (loss) per share (in dollars per share)	$ 0.08	$ (0.04)	$ 0.21	$ (0.11)