Stock Incentive Plans - Restricted Stock Awards (Details) - $ / shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Stock
Number of Units
Number of shares, Beginning Balance (in shares)	641,844	630,962	567,540
Number of shares, Granted (in shares)	162,806	349,091	324,502
Number of shares, Forfeited (in shares)	(21,534)	(51,061)	(16,669)
Number of shares, Vested (in shares)	(310,117)	(287,148)	(244,411)
Number of shares, Ending Balance (in shares)	472,999	641,844	630,962
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average grant date fair value, Beginning balance (in dollars per share)	$ 10.25	$ 10.66	$ 10.62
Weighted-average grant date fair value, Granted (in dollars per share)	10.38	10.19	11.19
Weighted-average grant date fair value, Forfeited (in dollars per share)	10.37	10.44	10.80
Weighted-average grant date fair value, Vested (in dollars per share)	10.08	11.02	11.29
Weighted-average grant date fair value, Ending balance (in dollars per share)	$ 10.40	$ 10.25	$ 10.66
Performance Shares
Number of Units
Number of shares, Beginning Balance (in shares)	781,923	785,797	686,684
Number of shares, Granted (in shares)	296,050	293,111	266,009
Number of shares, Forfeited (in shares)	(70,728)	(113,668)
Number of shares, Vested (in shares)	(251,375)	(218,514)	(200,374)
Number of shares, Ending Balance (in shares)	796,532	781,923	785,797
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted-average grant date fair value, Beginning balance (in dollars per share)	$ 11.19	$ 10.42	$ 10.65
Weighted-average grant date fair value, Granted (in dollars per share)	10.14	9.82	11.04
Weighted-average grant date fair value, Forfeited (in dollars per share)	9.93	9.86
Weighted-average grant date fair value, Vested (in dollars per share)	8.80	11.98	12.15
Weighted-average grant date fair value, Ending balance (in dollars per share)	$ 11.16	$ 11.19	$ 10.42

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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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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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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