Equity-based Compensation - Summary of Deferred Stock Unit Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deferred stock unit, share transfer obligation (in shares)	1
Deferred Stock Units
Stock Awards - Outstanding (in shares)	1,501,021
Stock Awards - Outstanding (in shares)		1,501,021
Weighted Average Award Date Fair Value
Weighted Average Award Date Fair Value - Outstanding (in Dollars per share)	$ 20.58
Weighted Average Award Date Fair Value - Outstanding (in Dollars per share)	$ 21.53	$ 20.58
Deferred Stock Units
Deferred Stock Units
Stock Awards - Outstanding (in shares)	253,445	247,219	221,471
Stock Awards - Awarded (in shares)	47,091	45,886	53,527
Shares distributed (in shares)	(30,559)	(39,660)	(27,779)
Stock Awards - Outstanding (in shares)	269,977	253,445	247,219
Weighted Average Award Date Fair Value
Weighted Average Award Date Fair Value - Outstanding (in Dollars per share)	$ 19.93	$ 19.92	$ 20.10
Awarded (in Dollars per share)	23.53	21.22	18.56
Shares distributed (in Dollars per share)	23.57	21.29	18.76
Weighted Average Award Date Fair Value - Outstanding (in Dollars per share)	$ 20.14	$ 19.93	$ 19.92
Expense recorded	$ 1.1	$ 1.0	$ 1.0
2016 Director Plan
Weighted Average Award Date Fair Value
Common stock available for equity-based compensation awards (in dollars per share)	117,261

Number of shares Company is obligated to transfer for each deferred stock unit

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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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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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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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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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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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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