Shareholders' Equity - Summary of Share Count and Par Value Data Related to Shareholders' Equity (Details) - $ / shares	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Preferred Stock
Preferred stock, par value per share	$ 0	$ 0		$ 0
Preferred stock, shares authorized	25,000,000	25,000,000		25,000,000
Preferred stock, shares outstanding	0	0		0
Common Stock
Common stock, par value per share	$ 0	$ 0		$ 0
Common stock, shares authorized	75,000,000	75,000,000		75,000,000
Common stock, shares issued	56,924,737	56,924,737		56,786,849
Common stock, shares outstanding	32,601,889	32,601,889	33,087,281	32,750,727	32,938,466
Treasury stock
Treasury stock, shares held	24,322,848	24,322,848		24,036,122
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	20,273	1,538

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Face amount per share of no-par value common stock.

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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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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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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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