Stockholders' Equity - Summary of Stockholders' Equity Capital Accounts (Details) - $ / shares	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Preferred Stock:
Authorized shares	50,000,000	50,000,000
Issued shares	0	14,375,000
Outstanding shares	0	14,369,965	14,370,060
Common Stock, $1.00 par value:
Par value (in USD per share)	$ 1.00	$ 1.00
Authorized shares	700,000,000	700,000,000
Issued shares	406,497,122	384,849,236
Outstanding shares	405,254,113	383,674,603

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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 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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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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