Employee Benefits and Share-Based Compensation - Performance Based Restricted Stock Units Awards (Details) - 2009 Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of compensation cost recognized	4 months 15 days	6 months
Fair value of restricted stock units	$ 1.1	$ 1.0	$ 1.1
Unrecognized compensation cost	$ 0.4	$ 0.4
Number of Shares
Outstanding and unvested December 31	36
Granted (Awarded)	36
Vested (Released)	(41)
Forfeited	0
Outstanding and unvested at December 31	31	36
Weighted-Average Grant Date Fair Value
Outstanding and unvested December 31	$ 26.47
Granted (Awarded)	36.05	$ 26.42	$ 18.20
Vested (Released)	26.48
Forfeited	0.00
Outstanding and unvested at December 31	$ 35.97	$ 26.47
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period of compensation cost recognized	1 year 2 months 12 days
Fair value of restricted stock units	$ 1.9	$ 1.5	$ 0.7
Unrecognized compensation cost	$ 1.5	$ 2.0
Number of Shares
Outstanding and unvested December 31	233
Granted (Awarded)	60
Vested (Released)	(107)
Forfeited	(35)
Outstanding and unvested at December 31	151	233
Weighted-Average Grant Date Fair Value
Outstanding and unvested December 31	$ 17.96
Granted (Awarded)	29.56	$ 20.94	$ 14.68
Vested (Released)	18.20
Forfeited	14.08
Outstanding and unvested at December 31	$ 23.33	$ 17.96

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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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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-Publisher FASB
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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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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Subparagraph (c)(2)(i)-(ii)
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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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-Publisher FASB
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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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