Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue:
Total revenue	$ 720.0	$ 451.7	$ 1,400.3	$ 855.4
Costs and expenses:
Cost of revenue	253.3	179.2	514.0	325.4
Research and development	109.8	227.9	250.5	425.8
Sales and marketing	244.2	134.7	492.9	257.8
General and administrative	37.9	39.2	73.6	67.4
Total costs and expenses	645.2	581.0	1,331.0	1,076.4
Income (loss) from operations	74.8	(129.3)	69.3	(221.0)
Interest income	1.7	3.6	3.4	9.1
Interest expense	(14.7)	(7.0)	(29.4)	(13.9)
Other income (expense), net	(9.1)	0.6	(0.2)	(1.7)
Income (loss) before income taxes	52.7	(132.1)	43.1	(227.5)
Provision for (benefit from) income taxes	24.9	18.2	38.3	26.7
Net income (loss)	$ 27.8	$ (150.3)	$ 4.8	$ (254.2)
Net income (loss) per share attributable to common stockholders:
Basic	$ 0.03	$ (0.16)	$ 0.00	$ (0.27)
Diluted	$ 0.02	$ (0.16)	$ 0.00	$ (0.27)
Weighted-average common shares used to compute net income (loss) per share attributable to common stockholders:
Basic	1,089.7	956.9	1,087.1	954.7
Diluted	1,147.6	956.9	1,146.0	954.7
Online Game [Member]
Revenue:
Total revenue	$ 587.0	$ 388.2	$ 1,144.0	$ 732.5
Advertising and Other [Member]
Revenue:
Total revenue	$ 133.0	$ 63.5	$ 256.3	$ 122.9