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Derivative liabilities and changes in fair value.

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Stock issued during period shares contingent consideration.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement.

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- Definition

Aggregate number of common shares reserved for future issuance.

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- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Date when the debt instrument is scheduled to be fully repaid, in YYYY-MM-DD format.

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Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of liabilities measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

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Amount of transfers of liabilities measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

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Fair Value Measurements - Additional Information (Details) € in Millions	1 Months Ended		3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2019 USD ($)	Nov. 30, 2017 USD ($)	Sep. 30, 2021 USD ($) shares	Sep. 30, 2021 EUR (€) shares	Jun. 30, 2021 shares	Sep. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	May 27, 2020 shares
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Asset impairment charges								$ 0
Fair value of assets transferred from level 1 to level 2			$ 0					0
Fair value of assets transferred from level 2 to level 1			0					0
Fair value of liabilities transferred from level 1 to level 2			0					0
Fair value of liabilities transferred from level 2 to level 1			$ 0					$ 0
Common stock reserved for future issuance \| shares			5,700,000					5,700,000
Increase (Decrease) in contingent consideration obligation								$ (7,046,000)	$ 1,500,000
0% Convertible Senior Notes Due March 15, 2026
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value of convertible senior notes			$ 421,500,000					421,500,000
Principal amount of notes			$ 375,000,000.0					$ 375,000,000.0
Debt instrument, interest rate			0.00%					0.00%
Debt instrument, maturity date								Mar. 15, 2026
0.125% Convertible Senior Notes Due 2024
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value of convertible senior notes			$ 670,100,000					$ 670,100,000		$ 663,600,000
Principal amount of notes	$ 450,000,000.0		$ 450,000,000					$ 450,000,000		450,000,000
Debt instrument, interest rate	0.125%		0.125%					0.125%
Debt instrument, maturity date	Dec. 15, 2024							Dec. 15, 2024
1.50% Convertible Senior Notes Due 2022
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value of convertible senior notes			$ 1,400,000					$ 1,400,000		265,500,000
Principal amount of notes		$ 115,000,000.0	$ 303,000					$ 303,000		79,795,000
Debt instrument, interest rate		1.50%	1.50%					1.50%
Debt instrument, maturity date		Nov. 01, 2022						Nov. 01, 2022
Techwan SA
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Common stock reserved for future issuance \| shares											6,779
Techwan SA \| Other Expense, Net
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Derivative liabilities, changes in fair value			$ 100,000			$ (100,000)
Techwan SA \| Maximum \| Other Expense, Net
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Derivative liabilities, changes in fair value								$ 100,000
One2Many Group B.V.
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Increase (Decrease) in contingent consideration obligation			$ 1,100,000					400,000
Cash paid net of cash acquired \| €				€ 4.1
Issuance of common stock for contingent consideration \| shares			41,668	41,668
SnapComms Limited
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Increase (Decrease) in contingent consideration obligation							$ 700,000
Issuance of common stock for contingent consideration \| shares					6,188
Red Sky Technologies Inc.
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Increase (Decrease) in contingent consideration obligation			$ (8,200,000)
Cash paid net of cash acquired			$ 400,000
Issuance of common stock for contingent consideration \| shares			4,058	4,058
Fair Value Measurements, Nonrecurring
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Asset impairment charges								$ 0		$ 0