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Stock-Based Compensation (Restricted Stock) (Details) - Restricted Stock [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted stock awards vested		$ 6.4	$ 8.8	$ 8.1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, shares, beginning balance		284,284
Nonvested, weighted-average grant date fair value, beginning balance (in dollars per share)		$ 53.11
Granted, shares	[1]	143,424
Granted, weighted-average grant date fair value (in dollars per share)	[1]	$ 52.23	$ 62.54	$ 52.87
Vested, shares		(128,640)
Vested, weighted-average grant date fair value (in dollars per share)		$ 49.26
Forfeited, shares		(32,162)
Forfeited, weighted-average grant date fair value (in dollars per share)		$ 55.23
Nonvested, shares, ending balance		266,906	284,284
Nonvested, weighted-average grant date fair value, ending balance (in dollars per share)		$ 54.23	$ 53.11
Awards Granted 2015 and 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)		4 years
AwardsGranted2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)		4 years
[1] The restricted stock awards granted during 2016 are primarily related to our employee annual restricted stock award grant in March 2016.

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- Definition

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.

+ References

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-Publisher FASB
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-Section 50
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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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