Schedule II Condensed Financial Information of Registrant (Parenthetical) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,000,000us-gaap_PreferredStockSharesAuthorized	1,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares issued	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	75,000,000us-gaap_CommonStockSharesAuthorized	75,000,000us-gaap_CommonStockSharesAuthorized
Common stock, shares issued	64,245,048us-gaap_CommonStockSharesIssued	63,629,105us-gaap_CommonStockSharesIssued
Treasury stock, shares	23,308,430us-gaap_TreasuryStockShares	23,117,554us-gaap_TreasuryStockShares	22,943,925us-gaap_TreasuryStockShares	22,028,030us-gaap_TreasuryStockShares
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	64,245,048	63,629,105
Treasury stock, shares	23,308,430	23,117,554

Face amount or stated value per share of common stock.

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-Name Accounting Standards Codification

-Topic 210

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

+ References

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-Publisher FASB

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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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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 common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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