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Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation [Abstract]
Number of common shares available for grant under the incentive plan (in shares)	749,265
Share-based compensation	$ 16,643	$ 13,345	$ 11,053
Tax benefits (expense) associated with stock-based compensation	$ 7,700	$ 5,300	4,600
Stock option activity [Roll Forward]
Outstanding, beginning balance (in shares)	28,000
Granted (in shares)	0
Exercised (in shares)	(20,000)
Canceled (in shares)	0
Outstanding, ending balance (in shares)	8,000	28,000
Exercisable, ending balance (in shares)	8,000
Weighted average exercise price [Abstract]
Outstanding, beginning balance (in dollars per share)	$ 29.56
Granted (in dollars per share)	0.00
Exercised (in dollars per share)	29.17
Canceled (in dollars per share)	0.00
Outstanding, ending balance (in dollars per share)	30.59	$ 29.56
Exercisable, ending balance (in dollars per share)	$ 30.59
Weighted average remaining contractual life, stock option awards outstanding at end of year (in years)	4 years 6 months
Weighted average remaining contractual life, stock option awards exercisable at end of year (in years)	4 years 6 months
Aggregate intrinsic value of options outstanding, ending balance	$ 315
Aggregate intrinsic value of options exercisable ending balance	315
Intrinsic value of options exercised during the year	$ 800	$ 300	$ 300
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	3 years
Employee Stock Purchase Plan (ESPP) [Abstract]
ESPP Stock Issued During Period (in shares)	17,000	24,000	37,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of shares vested during the year	$ 16,200	$ 18,600	$ 10,800
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 14,600
Unrecognized compensation expense, period for recognition (in months)	21 months
Equity Instruments Other than Options, Nonvested, Number of Shares[Roll Forward]
Balance at 12/31/2015 (in shares)	618,000
Granted (in shares)	236,000
Vested (in shares)	(333,000)
Canceled (in shares)	(18,000)
Balance at 12/31/2016 (in shares)	503,000	618,000
Weighted Average Grant Date Fair Value, Equity Instruments Other than Options [Abstract]
Balance at 12/31/2015 (in dollars per share)	$ 37.98
Granted (in dollars per share)	52.66	$ 51.54	$ 28.22
Vested (in dollars per share)	35.66
Canceled (in dollars per share)	44.66
Balance at 12/31/2016 (in dollars per share)	$ 46.17	37.98
Restricted Stock [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	3 years
Restricted Stock [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	5 years
Long-Term Incentive Program Awards [Member]
Weighted Average Grant Date Fair Value, Equity Instruments Other than Options [Abstract]
Balance at 12/31/2015 (in dollars per share)	$ 52.80
Granted (in dollars per share)	58.42
Vested (in dollars per share)	0.00
Canceled (in dollars per share)	52.80
Balance at 12/31/2016 (in dollars per share)	$ 56.04	$ 52.80
Long-Term Incentive Program Awards [Member] | Minimum [Member]
Equity Instruments Other than Options, Nonvested, Number of Shares[Roll Forward]
Balance at 12/31/2015 (in shares)	100,900
Granted (in shares)	133,380
Vested (in shares)	0
Canceled (in shares)	(2,550)
Balance at 12/31/2016 (in shares)	231,730	100,900
NumberofShareExpectedtoVestBasedOnCurrentEstimatesofPerformanceAchievment	302,059
Long-Term Incentive Program Awards [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards vesting period	3 years
Equity Instruments Other than Options, Nonvested, Number of Shares[Roll Forward]
Balance at 12/31/2015 (in shares)	201,800
Granted (in shares)	224,861
Vested (in shares)	0
Canceled (in shares)	(4,636)
Balance at 12/31/2016 (in shares)	422,025	201,800
2015LTIPAward [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 3,800
Equity Instruments Other than Options, Nonvested, Number of Shares[Roll Forward]
NumberofShareExpectedtoVestBasedOnCurrentEstimatesofPerformanceAchievment	178,770
2016LTIPAwards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 4,700
Equity Instruments Other than Options, Nonvested, Number of Shares[Roll Forward]
NumberofShareExpectedtoVestBasedOnCurrentEstimatesofPerformanceAchievment	123,289

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Employee Stock Purchase Plan (ESPP) [Abstract]

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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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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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.

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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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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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Net number of share options (or share units) granted during the period.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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No definition available.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term of exercisable stock options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Number of share options (or share units) exercised during the current period.

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