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

Name:	us-gaap_AllocatedShareBasedCompensationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Stock Compensation Plans - Allocation of Compensation Expense (Details) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) plan shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Plan information
Number of plans \| plan	2
Compensation expense
Total Compensation	$ 5,372	$ 4,871	$ 5,650
2009 Equity Incentive Plan
Plan information
Shares authorized for issuance \| shares	6,108
Percentage of Shares issued and outstanding	15.20%
Restricted Stock
Compensation expense
Total Compensation	$ 3,466	2,766	3,835
Long-term compensation plan
Compensation expense
Total Compensation	$ 1,906	$ 2,105	$ 1,815