Amount of letters of credit issued and reducing availability under revolving credit facility.

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Debt instrument covenant compliance leverage ratio actual.

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Debt instrument covenant compliance leverage ratio threshold.

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

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Contractual interest rate for funds borrowed, under the debt 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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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount of expense for amortization of deferred issuance costs associated with an own-share lending arrangement.

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Fixed interest rate related to the interest rate derivative.

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Nominal or face amount used to calculate payment on derivative.

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Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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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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Amount of loan with variable or adjustable rate of interest.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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Long-Term Debt - Additional Information (Detail)	3 Months Ended	12 Months Ended
Long-Term Debt - Additional Information (Detail)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)	Oct. 31, 2019 EUR (€)	Jul. 01, 2019	Feb. 08, 2019 USD ($)	Feb. 08, 2019 EUR (€)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity \| €							€ 220,000,000
Pre-tax gain from changes in currency exchange rates		$ 1,600,000
Interest rate on debt					1.25%
Debt instrument covenant compliance leverage ratio, threshold	4.5	4.0
Debt instrument covenant compliance leverage ratio, actual		2.2
Long-term debt, maturity date		Feb. 08, 2024
Amortization expense related to deferred debt issuance costs		$ 1,600,000
Other Assets [Member]
Debt Instrument [Line Items]
Unamortized deferred debt issuance costs	$ 2,400,000	$ 2,400,000
Floating-to-fixed Interest Rate Swap Agreement [Member]
Debt Instrument [Line Items]
Derivative notional amount \| €				€ 180,000,000
Derivative fixed interest rate				0.0395%
Loans variable rate of interest \| €				€ 180,000,000
Minimum [Member]
Debt Instrument [Line Items]
Long-term debt percentage bearing fixed Interest rate				0.00%
Term Loans [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity \| €			€ 220,000,000
5.375% Notes [Member]
Debt Instrument [Line Items]
Interest rate on debt	5.375%	5.375%	5.375%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity						$ 400,000,000
Federal fund rate spread		1.00%
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Federal fund rate spread		0.125%
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Federal fund rate spread		1.00%
Revolving Credit Facility [Member] \| Federal Funds Rate [Member]
Debt Instrument [Line Items]
Federal fund rate spread		0.50%
Revolving Credit Facility [Member] \| Euro Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Federal fund rate spread		1.125%
Revolving Credit Facility [Member] \| Euro Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Federal fund rate spread		2.00%
Revolving Credit Facility [Member] \| EURIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Federal fund rate spread		112.50%
Revolving Credit Facility [Member] \| EURIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Federal fund rate spread		200.00%
Letters of Credit [Member]
Debt Instrument [Line Items]
Letters of credit issued	$ 7,300,000	$ 7,300,000						$ 5,200,000
Letters of credit outstanding	$ 0	$ 0