Long-Term Debt (6.125% Senior Notes due 2021) - Additional Information (Detail) - 6.125% Senior Notes Due 2021 [Member] - USD ($)		3 Months Ended
Mar. 12, 2013	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Issued Senior Notes	$ 150,000,000.0
Debt instrument interest rate	6.125%	6.125%	6.125%
Debt instrument maturity date	Mar. 15, 2021
Interest on the notes		payable semi-annually in arrears on March 15 and September 15 of each year

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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- Definition

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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