Share-Based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Additional Disclosures [Abstract]
Total pre-tax share-based compensation expense (income) recognized in the Consolidated Statements of Earnings	$ 5,600	$ (700)	$ 500
Tax related benefits (expense)	$ 800	(200)	$ (300)
Adjustments to share-based compensation		$ 3,600
Non-vested Stock [Member]
Stock Unit Activity [Roll Forward]
Outstanding, beginning of period (in shares)	404	380	412
Granted (in shares)	142	134	142
Vested (in shares)	(27)	(46)	(111)
Cancelled (in shares)	(68)	(64)	(63)
Outstanding, end of period (in shares)	451	404	380
Grant Date Weighted Average Fair Value [Abstract]
Outstanding, beginning of period (in dollars per share)	$ 64.89	$ 66.02	$ 65.64
Granted (in dollars per share)	65.61	60.04	59.45
Vested (in dollars per share)	74.21	63.61	56.91
Cancelled (in dollars per share)	73.39	62.39	64.71
Outstanding, end of period (in dollars per share)	$ 63.28	$ 64.89	$ 66.02
Aggregate Intrinsic Value [Abstract]
Outstanding, aggregate intrinsic value	$ 33,283	$ 26,710	$ 21,239	$ 30,113
Additional Disclosures [Abstract]
Total intrinsic values of shares vested	1,400	$ 3,000	$ 7,700
Non-vested Stock and Performance Stock Units [Member]
Additional Disclosures [Abstract]
Compensation cost net yet recognized	$ 16,600
Compensation cost not yet recognized, period for recognition	2 years 4 months 2 days
2017 Stock Plan [Member] \| Non-vested Stock [Member]
Share-based Compensation Arrangement [Abstract]
Number of shares authorized for issuance (in shares)	1,800
Number of shares available for issuance (in shares)	1,200
Award vesting period	3 years
Percentage of grants to elected officers that will be performance stock unit awards	60.00%	100.00%	100.00%
Percentage of grants, non-vested restricted stock awards	40.00%
Number of years to measure performance metrics	3 years
2017 Stock Plan [Member] \| Non-vested Stock [Member] \| Maximum [Member]
Share-based Compensation Arrangement [Abstract]
Percentage of stated performance metrics award of grant	200.00%	200.00%	150.00%

The number of years to measure performance metrics in order to award performance stock unit awards.

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The future percentage of grants that will be performance stock unit awards.

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The percentage of grants that will be non-vested restricted stock awards.

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Stated performance metrics in an award of the original grant.

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Amount of increase (decrease) in additional paid in capital (APIC) resulting from a tax benefit (deficiency) associated with an share-based compensation plan other than an employee stock ownership plan (ESOP).

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Intrinsic value of outstanding award under share-based payment arrangement. Excludes share and unit options.

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