Debt Instrument, Discount Rate

No definition available.

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Namespace Prefix:	iclr_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

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

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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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+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Balance Type:	credit
Period Type:	instant

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Period Type:	instant

- Definition

Period between issuance and maturity of long-term debt, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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Namespace Prefix:	us-gaap_
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Period Type:	instant

- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

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Bank credit lines, loan facilities and notes - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended					12 Months Ended
	May 08, 2024	Mar. 31, 2026	Dec. 31, 2025	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2025	Nov. 26, 2025	May 02, 2023	Jul. 01, 2021
Debt Instrument [Line Items]
Drawdown of credit lines and loan facilities		$ 0				$ 50,000
Repayment		(7,440)				(57,440)
Long-term debt at fair value		$ 3,432,100	$ 3,500,100				$ 3,500,100
The New Notes \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 2,000,000
Debt discount paid	6,800
Senior Secured Notes (the "2027 Notes") \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 750,000
Debt instrument, interest rate (in percent)	5.809%	5.809%	5.809%				5.809%
Debt instrument, discount rate on underwriting (in percent)	0.00250
Senior Secured Notes (the "2029 Notes") \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 750,000
Debt instrument, interest rate (in percent)	5.849%	5.849%	5.849%				5.849%
Debt instrument, discount rate on underwriting (in percent)	0.00350
Senior Secured Notes (the "2034 Notes") \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount	$ 500,000
Debt instrument, interest rate (in percent)	6.00%	6.00%	6.00%				6.00%
Debt discount paid	$ 500
Debt instrument, discount rate on underwriting (in percent)	0.00450
Debt instrument, redemption price, percentage of principal amount redeemed	99.896%
Senior Secured Term Loan
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)							2.00%
Senior Secured Term Loan \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)							0.50%
Senior Secured Term Loan \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt instrument, principal amount										$ 5,515,000
Debt instrument, interest rate (in percent)		5.70%	5.672%				5.672%			1.00%
Senior Secured Revolving Loan
Debt Instrument [Line Items]
Long-term debt, term								7 years		5 years
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BB Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.35%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BB+ Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		1.00%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB- Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.75%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.55%
Senior Secured Revolving Loan \| Variable rate component two \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate \| Standard & Poor's, BBB+ Rating
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.40%
Senior Secured Revolving Loan \| Minimum \| Variable rate component one \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.00%
Senior Secured Revolving Loan \| Maximum \| Variable rate component one \| Base rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)		0.35%
Senior Secured Revolving Loan \| Senior Secured Revolving Loan \| Senior Secured Revolving Loan
Debt Instrument [Line Items]
Debt instrument, maximum borrowing capacity									$ 500,000	$ 300,000
Drawdown of credit lines and loan facilities		$ 0	$ 0	$ 0	$ 0	50,000	$ 50,000
Repayment		0	0	0	0	(50,000)	(50,000)
Long-term debt		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Senior Secured Credit Facility And Senior Secured Notes \| Senior Secured Term Loan
Debt Instrument [Line Items]
Debt discount paid										27,600
Senior Secured Notes \| Senior Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, principal amount										$ 500,000
Debt instrument, interest rate (in percent)										2.875%