Employee Benefit and Deferred Compensation Plans - Summary of the Changes in Restricted Stock (Details)	6 Months Ended
Jun. 30, 2019 $ / shares shares
Performance Shares
Performance-Based Restricted Stock
Beginning balance (shares) \| shares	41,300
Awarded (shares) \| shares	154,250
Vested (shares) \| shares	0
Cancelled (shares) \| shares	0
Ending balance (shares) \| shares	195,550
Weighted Average Grant-Date Fair Value
Beginning balance (usd per share) \| $ / shares	$ 40.89
Awarded (usd per share) \| $ / shares	30.18
Vested (usd per share) \| $ / shares	0
Cancelled (usd per share) \| $ / shares	0
Ending balance (usd per share) \| $ / shares	$ 32.44
Restricted Stock
Performance-Based Restricted Stock
Beginning balance (shares) \| shares	304,955
Awarded (shares) \| shares	267,859
Vested (shares) \| shares	(79,857)
Cancelled (shares) \| shares	(11,697)
Ending balance (shares) \| shares	481,260
Weighted Average Grant-Date Fair Value
Beginning balance (usd per share) \| $ / shares	$ 41.82
Awarded (usd per share) \| $ / shares	31.63
Vested (usd per share) \| $ / shares	38.95
Cancelled (usd per share) \| $ / shares	40.95
Ending balance (usd per share) \| $ / shares	$ 36.64

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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- 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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- 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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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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-Publisher FASB
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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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