Long-Term Debt (5.625% Senior Notes due 2023) - Additional Information (Detail) - 5.625% Senior Notes Due 2023 [Member] - USD ($)	6 Months Ended
Jun. 30, 2021	Dec. 31, 2020	Sep. 21, 2015	Feb. 11, 2015
Debt Instrument [Line Items]
Issued Senior Notes			$ 275,000,000.0	$ 375,000,000.0
Debt instrument interest rate	5.625%	5.625%	5.625%	5.625%
Senior Notes		$ 650,000,000	$ 650,000,000.0
Debt instrument maturity date	Feb. 15, 2023
Interest on the notes	payable semi-annually in arrears on February 15 and August 15 of each year
Debt instrument, redemption date	Mar. 17, 2021

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

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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