Stock Compensation Plans (Summary of Activity for Time-Based and Performance-Based RSUs) (Details)	9 Months Ended
Sep. 30, 2019 $ / shares shares
Time-Based RSUs Settled in Shares
Shares
Outstanding, at beginning of period (in shares)	1,121,391
Granted (in shares)	495,191
Vested (in shares)	(359,242)
Forfeited (in shares)	(68,511)
Outstanding, at end of period (in shares)	1,188,829
Weighted-Average Grant Date Fair Value
Outstanding, at beginning of period (in dollars per share) \| $ / shares	$ 51.22
Granted (in dollars per share) \| $ / shares	52.53
Vested (in dollars per share) \| $ / shares	31.62
Forfeited (in dollars per share) \| $ / shares	57.20
Outstanding, at end of period (in dollars per share) \| $ / shares	$ 57.34
Performance-Based RSUs Settled in Shares
Shares
Outstanding, at beginning of period (in shares)	411,290
Granted (in shares)	134,600
Vested (in shares)	(159,407)
Forfeited (in shares)	0
Outstanding, at end of period (in shares)	386,483
Weighted-Average Grant Date Fair Value
Outstanding, at beginning of period (in dollars per share) \| $ / shares	$ 49.93
Granted (in dollars per share) \| $ / shares	54.64
Vested (in dollars per share) \| $ / shares	29.18
Forfeited (in dollars per share) \| $ / shares	0
Outstanding, at end of period (in dollars per share) \| $ / shares	$ 60.13
Time-Based RSUs Settled in Cash
Shares
Outstanding, at beginning of period (in shares)	0
Granted (in shares)	12,145
Vested (in shares)	0
Forfeited (in shares)	(360)
Outstanding, at end of period (in shares)	11,785

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

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 (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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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).

+ References

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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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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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