Share-Based Payments Share-based Payments - Summary of Performance and Phantom Shares under 2013 Share Incentive Plan (Details) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding, end of period (in shares)	178,666
Phantom Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding, end of period (in shares)	113,727
2013 Share Incentive Plan \| Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding, beginning of period (in shares)	208,922	254,988	266,424
Granted (in shares)	215,273	216,878	278,477
Vested (in shares)	0	0	(87,059)
Forfeited (in shares)	(245,529)	(262,944)	(202,854)
Number of shares outstanding, end of period (in shares)	178,666	208,922	254,988
Number of shares outstanding, weighted average grant date fair value beginning of period (in dollars per share)	$ 38.71	$ 36.92	$ 24.17
Granted, weighted average grant date fair value (in dollars per share)	30.20	47.30	34.44
Vested, weighted average grant date fair value (in dollars per share)	0.00	0.00	37.30
Forfeited, weighted average grant date fair value (in dollars per share)	36.73	40.32	36.93
Number of shares outstanding, weighted average grant date fair value end of period (in dollars per share)	$ 38.71	$ 38.71	$ 36.92
2013 Share Incentive Plan \| Phantom Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares outstanding, beginning of period (in shares)	118,680	131,464	130,319
Granted (in shares)	150,185	173,619	147,513
Vested (in shares)	0	0	(36,159)
Forfeited (in shares)	(155,138)	(186,403)	(110,209)
Number of shares outstanding, end of period (in shares)	113,727	118,680	131,464
Number of shares outstanding, weighted average grant date fair value beginning of period (in dollars per share)	$ 38.71	$ 35.90	$ 38.75
Granted, weighted average grant date fair value (in dollars per share)	30.20	47.30	34.44
Vested, weighted average grant date fair value (in dollars per share)	0.00	0.00	36.96
Forfeited, weighted average grant date fair value (in dollars per share)	35.76	40.32	36.96
Number of shares outstanding, weighted average grant date fair value end of period (in dollars per share)	$ 36.46	$ 38.71	$ 35.90

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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- Definition

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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- Definition

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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- 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.

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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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Weighted average grant-date fair value of non-vested options forfeited.

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