Share-Based Compensation - Summary of Restricted Stock and Performance Unit Award Activity (Details)	6 Months Ended
Jun. 30, 2019 $ / shares shares
Restricted Stock
Restricted Stock and Performance Units [Roll Forward]
Outstanding at January 1, 2019 \| shares	743,591
Granted \| shares	199,185
Vested \| shares	(198,292)
Forfeitures \| shares	(6,530)
Outstanding at June 30, 2019 \| shares	737,954
Restricted Stock and Performance Units (Weighted Average Grant-date Fair Value) [Abstract]
Weighted Average Grant-Date Fair Value, Outstanding at January 1, 2019 \| $ / shares	$ 86.90
Weighted Average Grant-Date Fair Value, Granted \| $ / shares	95.45
Weighted Average Grant-Date Fair Value, Vested \| $ / shares	67.62
Weighted Average Grant-Date Fair Value, Forfeitures \| $ / shares	102.74
Weighted Average Grant-Date Fair Value, Outstanding at June 30, 2019 \| $ / shares	$ 94.25
Performance Units
Restricted Stock and Performance Units [Roll Forward]
Outstanding at January 1, 2019 \| shares	266,704
Granted \| shares	115,608
Vested \| shares	(59,165)
Outstanding at June 30, 2019 \| shares	323,147
Restricted Stock and Performance Units (Weighted Average Grant-date Fair Value) [Abstract]
Weighted Average Grant-Date Fair Value, Outstanding at January 1, 2019 \| $ / shares	$ 90.01
Weighted Average Grant-Date Fair Value, Granted \| $ / shares	96.98
Weighted Average Grant-Date Fair Value, Vested \| $ / shares	67.84
Weighted Average Grant-Date Fair Value, Outstanding at June 30, 2019 \| $ / shares	$ 96.56

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=109197908&loc=d3e5070-113901

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- Definition

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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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).

+ References

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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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- Definition

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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 2
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- Definition

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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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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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

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.

+ References

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