Equity - Restricted Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Restricted stock
Restricted stock awards
Cancelled (in shares)	15,400	640
Compensation expense related to share-based award	$ 3,965	$ 3,138
Performance-based stock units
Restricted stock awards
Cancelled (in shares)	8,706
Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted	143,057	127,087
Nonvested awards
Remaining compensation expense	$ 7,637
2017 \| Restricted stock
Nonvested awards
Remaining compensation expense	1,282
2018 \| Restricted stock
Nonvested awards
Remaining compensation expense	3,947
2019 \| Restricted stock
Nonvested awards
Remaining compensation expense	2,149
2020 \| Restricted stock and performance-based stock units
Nonvested awards
Remaining compensation expense	$ 259
Grant Date Price $45.76 \| Three year vesting \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted	74,760
Granted (in dollars per share)	$ 45.76
Vesting period	3 years
Grant Date Price $45.76 \| TSR Targets \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted	57,881
Granted (in dollars per share)	$ 45.76
Vesting period	4 years
Grant Date Price $45.76 \| Accelerated TSR Targets \| Restricted stock and performance-based stock units
Restricted stock awards
Vesting period	3 years
Grant Date Price $48.55 \| Vesting Date, June 1, 2018 \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted	7,416
Granted (in dollars per share)	$ 48.55
Grant Date Price $50.50 \| Three year vesting \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted	3,000
Granted (in dollars per share)	$ 50.50
Vesting period	3 years
Grant Date Price $43.24 \| Three year vesting \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted		65,300
Granted (in dollars per share)		$ 43.24
Vesting period		3 years
Grant Date Price $46.87 \| TSR Targets \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted		54,107
Granted (in dollars per share)		$ 46.87
Vesting period		3 years 8 months 12 days
Grant Date Price $46.87 \| Accelerated TSR Targets \| Restricted stock and performance-based stock units
Restricted stock awards
Vesting period		2 years 8 months 12 days
Grant Date Price $46.87 \| Vesting Date, June 1, 2017 \| Restricted stock and performance-based stock units
Restricted stock awards
Number of shares granted		7,680
Granted (in dollars per share)		$ 46.87

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

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

+ 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=96867065&loc=d3e5070-113901

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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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No definition available.

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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)
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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
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
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- Definition

Number of shares under non-option equity instrument agreements that were either cancelled or expired.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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