Capped Call Transaction Cost

No definition available.

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Namespace Prefix:	alrm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt Instrument, Amount Outstanding Threshold, Not Subject To Redemption

+ References

No definition available.

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Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Convertible, Threshold Percentage Of Last Reported Sale Price

+ References

No definition available.

+ Details

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- Definition

Number Of Business Days

+ References

No definition available.

+ Details

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- Definition

Number Of Consecutive Trading Days

+ References

No definition available.

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- Definition

The price per share of the conversion feature embedded in the debt instrument.

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- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Period Type:	duration

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

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- Definition

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

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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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- Definition

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

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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- Definition

Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

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Price of a single share of a number of saleable stocks of a company.

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Number of shares that have been repurchased during the period and are being held in treasury.

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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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Debt, Commitments and Contingencies - Convertible Senior Notes (Details)			3 Months Ended					9 Months Ended
	May 31, 2024 USD ($) day $ / shares shares	Jan. 20, 2021 USD ($) day $ / shares	Sep. 30, 2025 USD ($) $ / shares shares	Jun. 30, 2025 USD ($) shares	Mar. 31, 2025 USD ($) shares	Sep. 30, 2024 shares	Jun. 30, 2024 USD ($) shares	Sep. 30, 2025 USD ($) $ / shares shares	Sep. 30, 2024 USD ($) shares	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Proceeds from convertible debt								$ 0	$ 500,000,000
Share price (in dollars per share) \| $ / shares			$ 53.08					$ 53.08
Capped call transaction cost	$ 63,100,000
Purchases of treasury stock			$ 12,289,000	$ 5,105,000	$ 5,062,000		$ 75,559,000
Purchases of treasury stock (in shares) \| shares			225,094			0		399,494	1,117,068
Treasury Stock
Debt Instrument [Line Items]
Purchases of treasury stock	$ 75,000,000		$ 12,252,000	$ 5,108,000	$ 5,059,000		$ 75,000,000
Purchases of treasury stock (in shares) \| shares	1,117,068		225,000	88,000	86,000		1,117,000
Convertible Senior Notes Due 2026
Debt Instrument [Line Items]
Proceeds from convertible debt		$ 484,300,000
Debt issuance costs		$ 15,700,000
Debt instrument, redemption price, percentage		100.00%
Conversion ratio		0.0067939
Conversion price (in dollars per share) \| $ / shares		$ 147.19
Convertible Senior Notes Due 2026 \| Redemption period one
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage		100.00%
Threshold percentage stock price trigger		130.00%
Trading days threshold \| day		20
Consecutive trading days threshold \| day		30
Convertible Senior Notes Due 2026 \| Redemption period two
Debt Instrument [Line Items]
Threshold percentage stock price trigger		130.00%
Trading days threshold \| day		20
Consecutive trading days threshold \| day		30
Number of business days \| day		5
Number of consecutive trading days \| day		10
Percentage of last reported sale price threshold		98.00%
Convertible Senior Notes Due 2026 \| Senior Notes
Debt Instrument [Line Items]
Debt instrument, face amount		$ 500,000,000.0	$ 500,000,000.0					$ 500,000,000.0
Debt instrument, interest rate		0.00%
Effective interest rate		0.60%
Debt instrument, fair value			492,000,000.0					492,000,000.0		$ 473,800,000
2017 Facility \| Line of Credit \| Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt		$ 110,000,000.0
Convertible Senior Notes Due 2029
Debt Instrument [Line Items]
Proceeds from convertible debt	$ 485,200,000
Debt issuance costs	$ 14,800,000
Debt instrument, redemption price, percentage	100.00%
Conversion ratio	0.0114571
Conversion price (in dollars per share) \| $ / shares	$ 87.28
Convertible Senior Notes Due 2029 \| Redemption period one
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage	100.00%
Threshold percentage stock price trigger	130.00%
Trading days threshold \| day	20
Consecutive trading days threshold \| day	30
Debt instrument, amount outstanding threshold, not subject to redemption	$ 75,000,000.0
Convertible Senior Notes Due 2029 \| Redemption period two
Debt Instrument [Line Items]
Threshold percentage stock price trigger	130.00%
Trading days threshold \| day	20
Consecutive trading days threshold \| day	30
Number of business days \| day	5
Number of consecutive trading days \| day	10
Percentage of last reported sale price threshold	98.00%
Convertible Senior Notes Due 2029 \| Senior Notes
Debt Instrument [Line Items]
Debt instrument, face amount	$ 500,000,000.0		500,000,000					500,000,000
Debt instrument, interest rate	2.25%
Effective interest rate	2.90%
Debt instrument, fair value			$ 479,400,000					$ 479,400,000		$ 496,700,000