Amount of additional stock repurchase plan authorization.

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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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Face amount or stated value per share of common stock.

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The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Number of shares issued for each share of convertible preferred stock that is converted.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Number of shares issued under share-based payment arrangement.

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Number of shares issued which are neither cancelled nor held in the treasury.

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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Number of shares that have been repurchased during the period and are being held in treasury.

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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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Shareholders' Equity (Details) - USD ($)	12 Months Ended			69 Months Ended
Shareholders' Equity (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Mar. 31, 2015	Dec. 31, 2011	Dec. 31, 2008
Class of Stock [Line Items]
Common stock, shares authorized (shares)	195,000,000	195,000,000		195,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01		$ 0.01
Common stock, shares issued (shares)	97,242,318	96,372,182		97,242,318
Preferred stock, shares authorized (shares)	5,000,000	5,000,000		5,000,000
Preferred stock, shares issued (shares)							160,000
Conversion of convertible preferred stock (shares)	100			100
Liquidation preference (in dollars per share)	$ 0.01			$ 0.01
Authorized repurchase amount	$ 130,000,000.0			$ 130,000,000.0		$ 60,000,000.0
Additional repurchase amount					$ 70,000,000.0
Repurchase of common stock (shares)	7,186,521			0
Treasury stock acquired, aggregate purchase price	$ 86,300,000
Remaining authorized repurchase amount	$ 43,700,000			$ 43,700,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)		88,103,440
Ending balance (shares)			88,103,440
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)	67,323	71,967	74,364
Conversion of convertible preferred stock (shares)	(3,734)	(4,644)	(2,397)
Ending balance (shares)	63,589	67,323	71,967	63,589
Treasury
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)	7,186,521	7,186,521	7,186,521
Ending balance (shares)	7,186,521	7,186,521	7,186,521	7,186,521
Common stock
Class of Stock [Line Items]
Common stock, shares outstanding (shares)	90,055,797			90,055,797
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (shares)	89,185,661		87,544,777
Conversion of convertible preferred stock (shares)	373,416	464,431	239,748
Issuance for share-based compensation plans (shares)	496,720	617,790	318,915
Ending balance (shares)	90,055,797	89,185,661		90,055,797