Share-Based Payments - Stock incentive awards to executive officers (Details)	9 Months Ended
Sep. 30, 2016 $ / shares shares
Stock Performance Awards \| Executive Officers \| February 4, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units Granted \| shares	81,500
Grant-Date Fair Value per Award \| $ / shares	$ 24.03
Vesting Date	December 31, 2018
Restricted Stock Units \| Executive Officers \| February 4, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units Granted \| shares	22,000
Grant-Date Fair Value per Award \| $ / shares	$ 28.915
Vesting Percentage	25.00%
Vesting Date	February 6, 2020
Restricted Stock Units \| Key Employees \| April 11, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units Granted \| shares	15,800
Grant-Date Fair Value per Award \| $ / shares	$ 24
Vesting Percentage	100.00%
Vesting Date	April 8, 2020
Restricted Stock Units \| Key Employees \| September 21, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units Granted \| shares	1,420
Grant-Date Fair Value per Award \| $ / shares	$ 30.59
Vesting Percentage	100.00%
Vesting Date	April 8, 2020
Restricted Stock \| Nonemployee Directors \| April 11, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares/Units Granted \| shares	23,200
Grant-Date Fair Value per Award \| $ / shares	$ 28.66
Vesting Percentage	25.00%
Vesting Date	April 8, 2020

Share Based Compensation Arrangement by Share Based Payment Award, Award Vesting Date

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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
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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

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- Definition

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.

+ References

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- Definition

Percentage of vesting of 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 (a)(1)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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