Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Revision of Prior Period Change in Accounting Principle Adjustment [Member]	RSUs [Member]	Class A Common stock [Member]	Class A Common stock [Member] RSUs [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Treasury Stock [Member] RSUs [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Revision of Prior Period Change in Accounting Principle Adjustment [Member]
Beginning balance, Value at Dec. 31, 2019	$ 1,975.4					$ 3,898.7			$ (125.9)	$ (1,797.4)
Beginning balance, Shares at Dec. 31, 2019				950,000,000.0
Exercise of stock options and ESPP	8.8					8.8
Exercise of stock options and ESPP, Shares				2,500,000
Vesting of RSUs, net of tax withholdings			$ (14.8)					$ (14.8)
Vesting of RSUs, net of tax withholdings, Shares					3,300,000
Stock-based compensation expense	20.5					20.5
Retirements of treasury stock							$ 14.8			(14.8)
Adoption of ASU 2016-13 | 2016-13		$ (0.4)									$ (0.4)
Net income (loss)	(103.9)									(103.9)
Other comprehensive income (loss)	(30.0)								(30.0)
Ending balance, Value at Mar. 31, 2020	1,855.6					3,928.0			(155.9)	(1,916.5)
Ending balance, Shares at Mar. 31, 2020				955,800,000
Beginning balance, Value at Dec. 31, 2019	1,975.4					3,898.7			(125.9)	(1,797.4)
Beginning balance, Shares at Dec. 31, 2019				950,000,000.0
Net income (loss)	(254.2)
Other comprehensive income (loss)	(12.3)
Ending balance, Value at Jun. 30, 2020	1,736.2					3,955.5			(138.2)	(2,081.1)
Ending balance, Shares at Jun. 30, 2020				958,800,000
Beginning balance, Value at Mar. 31, 2020	1,855.6					3,928.0			(155.9)	(1,916.5)
Beginning balance, Shares at Mar. 31, 2020				955,800,000
Exercise of stock options and ESPP	1.9					1.9
Exercise of stock options and ESPP, Shares				600,000
Vesting of RSUs, net of tax withholdings			(14.3)					(14.3)
Vesting of RSUs, net of tax withholdings, Shares					2,400,000
Stock-based compensation expense	25.6					25.6
Retirements of treasury stock							14.3			(14.3)
Net income (loss)	(150.3)									(150.3)
Other comprehensive income (loss)	17.7								17.7
Ending balance, Value at Jun. 30, 2020	1,736.2					3,955.5			(138.2)	(2,081.1)
Ending balance, Shares at Jun. 30, 2020				958,800,000
Beginning balance, Value at Dec. 31, 2020	2,941.5					5,276.5			(50.7)	(2,284.3)
Beginning balance, Shares at Dec. 31, 2020				1,081,600,000
Exercise of stock options and ESPP	10.5					10.5
Exercise of stock options and ESPP, Shares				2,700,000
Vesting of RSUs, net of tax withholdings			(8.2)					(8.2)
Vesting of RSUs, net of tax withholdings, Shares					4,500,000
Stock-based compensation expense	37.2					37.2
Retirements of treasury stock							8.2			(8.2)
Net income (loss)	(23.0)									(23.0)
Other comprehensive income (loss)	(15.6)								(15.6)
Ending balance, Value at Mar. 31, 2021	2,942.4					5,324.2			(66.3)	(2,315.5)
Ending balance, Shares at Mar. 31, 2021				1,088,800,000
Beginning balance, Value at Dec. 31, 2020	2,941.5					5,276.5			(50.7)	(2,284.3)
Beginning balance, Shares at Dec. 31, 2020				1,081,600,000
Net income (loss)	4.8
Other comprehensive income (loss)	(4.6)								(4.6)
Ending balance, Value at Jun. 30, 2021	3,020.6					5,367.6			(55.3)	(2,291.7)
Ending balance, Shares at Jun. 30, 2021				1,092.0
Beginning balance, Value at Mar. 31, 2021	2,942.4					5,324.2			(66.3)	(2,315.5)
Beginning balance, Shares at Mar. 31, 2021				1,088,800,000
Exercise of stock options and ESPP	0.2					0.2
Exercise of stock options and ESPP, Shares				100,000
Vesting of RSUs, net of tax withholdings			$ (4.0)					$ (4.0)
Vesting of RSUs, net of tax withholdings, Shares					3,100,000
Stock-based compensation expense	43.2					43.2
Retirements of treasury stock							$ 4.0			(4.0)
Net income (loss)	27.8									27.8
Other comprehensive income (loss)	11.0								11.0
Ending balance, Value at Jun. 30, 2021	$ 3,020.6					$ 5,367.6			$ (55.3)	$ (2,291.7)
Ending balance, Shares at Jun. 30, 2021				1,092.0