Share-Based Payments (Narrative) (Details) - USD ($)		9 Months Ended
Mar. 01, 2018	Sep. 30, 2018
Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs		$ 6,485,000
Senior Executive and Employee Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Market value of shares vested and released	$ 31.35
Share unit liability	$ 1,400,000
Share unit liability, fair value attributable to past service	$ 6,701,000
Sign-on Grant Performance Share Unit Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Modified Performance Vesting Conditions, Weighted Average Fair Value		$ 43.34
Modified Performance Vesting Conditions, Incremental Compensation Recognized		$ 838,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of options granted		$ 7.68
Unrecognized compensation costs, period for recognition		2 years 1 month 6 days
Performance Share Units, Equity Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs		$ 9,597,000
Unrecognized compensation costs, period for recognition		1 year 9 months 18 days
Restricted Stock Units, Liability Classified Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs		$ 6,000
Unrecognized compensation costs, period for recognition		1 month 6 days
Restricted Stock Units, Equity Classified [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs		$ 4,540,000
Unrecognized compensation costs, period for recognition		2 years 3 months 18 days
Deferred Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs		$ 0

Modified Performance Vesting Conditions, Incremental Compensation Recognized

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Modified Performance Vesting Conditions, Weighted Average Fair Value

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grant Date Fair Value

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- Definition

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. Additionally, share-based awards which were paid or settled.

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No definition available.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
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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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- Definition

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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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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- Definition

Intrinsic value of equity-based compensation awards outstanding. Excludes stock and unit options.

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