Percentage points added to the federal funds rate to compute the base rate

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Percentage points added to the Eurodollar rate on the debt instrument.

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Consolidated Leverage Ratio to remain compliant with credit agreement.

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Temporarily increased consolidated leverage ratio upon completion of an acquisition.

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Dollar amount threshold to qualify as an acquisition to trigger a temporary increase in the consolidated leverage ratio.

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- Definition

Early repayment of debt due in 2022

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Early repayment of debt due in 2023

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- Definition

Term loan principal repayment rate, increased

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Term loan principal repayment rate, initial

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

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No definition available.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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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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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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No definition available.

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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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Weighted average interest rate of long-term debt outstanding calculated over time.

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No definition available.

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Weighted average interest rate of long-term debt outstanding calculated at point in time.

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

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Debt (Details) - USD ($)	12 Months Ended
Debt (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 01, 2020	Nov. 01, 2019
Line of Credit Facility [Line Items]
Unsecured debt	$ 798,100,000	$ 498,500,000
Term loan principal repayment rate, initial	1.25%
Term loan principal repayment rate, increased	2.50%
Early debt repayment	$ 75,000,000.0
Early repayment of debt due in 2022	25,000,000.0
Early repayment of debt due in 2023	$ 50,000,000.0
Weighted-average interest rate over time	2.09%	2.96%
Consolidated leverage ratio	3.50
Consolidated leverage ratio increased	4.00
Qualified acquisition amount	$ 250,000,000.0
Unamortized debt issuance cost	$ 1,900,000	$ 1,500,000
Livermore Software Technology Corporation
Line of Credit Facility [Line Items]
Unsecured debt				$ 500,000,000.0
Weighted-average interest rate at a point in time	1.38%
Analytical Graphics, Inc.
Line of Credit Facility [Line Items]
Unsecured debt			$ 375,000,000.0
Weighted-average interest rate at a point in time	1.50%
Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 500,000,000.0
Outstanding borrowings under the credit agreement	0
Letter of Credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000.0
Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on federal funds rate	0.50%
Debt instrument, basis spread on Eurodollar rate	1.00%
Base Rate \| Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.125%
Base Rate \| Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.75%
Eurodollar \| Minimum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.125%
Eurodollar \| Maximum
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.75%