Share-Based Compensation Summary of the Corporation's Restricted Stock Unit Activity and Related Information (Details) - Restricted Stock Units (RSUs) shares in Thousands	12 Months Ended
Dec. 31, 2018 $ / shares shares
Service-Based Units
Non-vested shares outstanding at January 1, 2018 \| shares	199
Non-vested shares granted \| shares	194
Non-vested shares forfeited \| shares	26
Shares vested \| shares	0
Non-vested shares outstanding at December 31, 2018 \| shares	367
Non-vested shares outstanding at January 1, 2017 (Weighted-average grant-date fair value) \| $ / shares	$ 43.00
Non-vested shares granted (Weighted-average grant-date fair value) \| $ / shares	96.55
Non-vested shares forfeited (Weighted-average grant-date fair value) \| $ / shares	86.54
Shares vested (Weighted-average grant-date fair value) \| $ / shares	0.00
Non-vested shares outstanding at December 31, 2017 (Weighted-average grant-date fair value) \| $ / shares	$ 68.14
Performance-Based Units
Non-vested shares outstanding at January 1, 2018 \| shares	718
Non-vested shares granted \| shares	184
Non-vested shares forfeited \| shares	1
Shares vested \| shares	(239)
Non-vested shares outstanding at December 31, 2018 \| shares	662
Non-vested shares outstanding at January 1, 2017 (Weighted-average grant-date fair value) \| $ / shares	$ 42.39
Non-vested shares granted (Weighted-average grant-date fair value) \| $ / shares	92.80
Non-vested shares forfeited (Weighted-average grant-date fair value) \| $ / shares	93.26
Shares vested (Weighted-average grant-date fair value) \| $ / shares	41.59
Non-vested shares outstanding at December 31, 2017 (Weighted-average grant-date fair value) \| $ / shares	$ 56.64

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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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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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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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