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

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- Definition

Debt instrument covenant compliance leverage ratio actual.

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No definition available.

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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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No definition available.

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

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Description of the frequency of periodic payments (monthly, quarterly, annual).

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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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Description of debt redemption features under terms of the debt agreement.

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End date of debt instrument redemption period, in CCYY-MM-DD format.

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

+ References

No definition available.

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

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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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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)				1 Months Ended	12 Months Ended
Long-Term Debt - Additional Information (Detail)	Feb. 08, 2019 USD ($)	Sep. 07, 2018	Feb. 01, 2017	Dec. 31, 2019	Dec. 31, 2018 USD ($)	Jan. 31, 2019	Dec. 31, 2017 USD ($)	Oct. 03, 2012 USD ($)
Debt Instrument [Line Items]
Debt instrument covenant compliance leverage ratio, threshold					4.5
Debt instrument covenant compliance leverage ratio, actual					2.9
Amortization expense related to deferred debt issuance costs					$ 1,100,000
Other Assets [Member]
Debt Instrument [Line Items]
Unamortized deferred debt issuance costs					$ 1,900,000
5.375% Notes [Member]
Debt Instrument [Line Items]
Long-term debt, maturity date					Oct. 15, 2020
Aggregate principal amount								$ 250,000,000
Interest rate on debt					5.375%			5.375%
Frequency of interest payable					Semiannually
Debt instrument redemption					The 5.375% Notes are redeemable, in whole or in part, at any time on or after October 15, 2016 at the redemption prices specified in the applicable Indenture.
Debt instrument redemption date					Feb. 28, 2019
5.375% Notes [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Interest rate on debt						5.375%
Five-year Term Loan [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 220,000,000
Debt Instrument, Term	5 years
Scenario, Forecast [Member]
Debt Instrument [Line Items]
Debt instrument covenant compliance leverage ratio, threshold				4.0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity					$ 400,000,000
Long-term debt, maturity date					Mar. 12, 2020
Debt instrument covenant compliance leverage ratio, threshold		4.0	4.0
Federal fund rate spread					1.00%
Revolving Credit Facility [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 400,000,000
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] \| Daily Euro Rate [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Federal fund rate spread					1.125%
Revolving Credit Facility [Member] \| Daily Euro Rate [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Federal fund rate spread					2.00%
Letters of Credit [Member]
Debt Instrument [Line Items]
Letters of credit issued					$ 5,200,000		$ 5,200,000
Letters of credit outstanding					$ 0