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Equity - Shareholders' Equity (Details) - shares | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Movement in Common Stock and Treasury Stock [Roll Forward] |  |  |
Balance January 1 (in shares) | 3,577,103,522 |  |
Balance December 31 (in shares) | 3,577,103,522 | 3,577,103,522 |
Common Stock |  |  |
Movement in Common Stock and Treasury Stock [Roll Forward] |  |  |
Balance January 1 (in shares) | 3,577,000,000 | 3,577,000,000 | 3,577,000,000
Purchases of treasury stock (in shares) | 0 | 0 | 0
Issuances (in shares) | 0 | 0 | 0
Balance December 31 (in shares) | 3,577,000,000 | 3,577,000,000 | 3,577,000,000
Treasury Stock |  |  |
Movement in Common Stock and Treasury Stock [Roll Forward] |  |  |
Balance January 1 (in shares) | 880,000,000 | 828,000,000 | 796,000,000
Purchases of treasury stock (in shares) | 122,000,000 | 67,000,000 | 60,000,000
Issuances (in shares) | (17,000,000) | (15,000,000) | (28,000,000)
Balance December 31 (in shares) | 985,000,000 | 880,000,000 | 828,000,000

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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 (or other type of equity) issued during the period as a result of any equity-based compensation plan other than an employee stock ownership plan (ESOP), net of any shares forfeited. Shares issued could result from the issuance of restricted stock, the exercise of stock options, stock issued under employee stock purchase plans, and/or other employee benefit plans. + 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(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: 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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