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Equity Equity (Common Stock Changes in Number of Shares Issued, Held in Treasury and Oustanding) (Details) - shares | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Class of Stock [Line Items] |  |  |  |  |
Common Stock, Shares, Issued |  | 79,137,758 | 79,137,758 |  |
Treasury Stock, Shares, Acquired |  |  |  | (1,356,892) |
Common Stock Issuable [Member] |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Common Stock, Shares, Issued |  | 79,137,758 | 79,137,758 | 79,137,758 | 79,137,758
Stock Based Compensation Shares | [1] | 0 | 0 | 0 |
Treasury Stock, Shares, Acquired |  | 0 | 0 | 0 |
Common Stock Held In Treasury [Member] |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Common Stock, Shares, Issued |  | 16,323,390 | 14,685,663 | 14,835,256 | 13,933,232
Stock Based Compensation Shares | [1] | (294,328) | (358,273) | (454,868) |
Treasury Stock, Shares, Acquired |  | (1,932,055) | (208,680) | (1,356,892) |
Common Stock Outstanding [Member] |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Common Stock, Shares, Issued |  | 62,814,368 | 64,452,095 | 64,302,502 | 65,204,526
Stock Based Compensation Shares | [1] | (294,328) | (358,273) | (454,868) |
Treasury Stock, Shares, Acquired |  | (1,932,055) | (208,680) | (1,356,892) |
[1] | Represents net shares issued from treasury pursuant to the Company’s stock-based compensation programs.

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- Definition 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. + References No definition available. + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Number of shares that have been repurchased during the period and are being held in treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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