Stock-Based Compensation - RSA, RSU (Details) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($) $ / shares shares
Weighted Average Grant Date Fair Value
Expense recognition period	4 years
Restricted Stock Awards
Number of Shares
Number of Shares, Restricted Stock outstanding, Beginning Balance \| shares	47,235
Number of Shares, Vested \| shares	(22,750)
Number of Shares, Restricted Stock outstanding, Ending Balance \| shares	24,485
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance \| $ / shares	$ 27.36
Weighted Average Grant Date Fair Value, Vested \| $ / shares	26.30
Weighted Average Grant Date Fair Value, Ending Balance \| $ / shares	$ 28.35
Stock incentive plan, vesting period	1 year
Unrecognized compensation expense \| $	$ 0.4
Earned Restricted Stock Units [Member]
Number of Shares
Number of Shares, Restricted Stock outstanding, Beginning Balance \| shares	891,439
Number of Shares, Granted \| shares	466,528
Number of Shares, Vested \| shares	(382,964)
Number of Shares, Forfeited \| shares	(13,179)
Number of Shares, Restricted Stock outstanding, Ending Balance \| shares	961,824
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning Balance \| $ / shares	$ 37.85
Weighted Average Grant Date Fair Value, Granted \| $ / shares	37.13
Weighted Average Grant Date Fair Value, Vested \| $ / shares	34.97
Weighted Average Grant Date Fair Value, Forfeited \| $ / shares	36.27
Weighted Average Grant Date Fair Value, Ending Balance \| $ / shares	$ 38.67
Unrecognized compensation expense \| $	$ 18.4
Weighted-average period for recognition of compensation cost	2 years 3 months 18 days
Unearned Restricted Stock Units [Member]
Number of Shares
Number of Shares, Granted \| shares	189,815
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Granted \| $ / shares	$ 35.65
Vesting Two Years From January 31 of Grant Year \| Restricted Stock Units
Weighted Average Grant Date Fair Value
Stock incentive plan, vesting period	24 months
Vesting percentage	50.00%
Vesting Three Years From January 31 of Grant Year \| Restricted Stock Units
Weighted Average Grant Date Fair Value
Stock incentive plan, vesting period	36 months
Vesting percentage	25.00%
Vesting Four Years From January 31 of Grant Year \| Restricted Stock Units
Weighted Average Grant Date Fair Value
Stock incentive plan, vesting period	48 months
Vesting percentage	25.00%

Share-based Compensation Arrangement by Share-based Payment Award, Expense Recognition Period

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ 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 (i)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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.

+ References

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ 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 (a)(1)
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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
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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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)
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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).

+ 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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-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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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.

+ References

No definition available.

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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
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-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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No definition available.

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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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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)(2)
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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.

+ 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)(2)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Percentage of vesting of share-based compensation awards.

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

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