Dividends (Details) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended
Jun. 15, 2018	Mar. 16, 2018	Jun. 30, 2018	Jun. 30, 2017
Dividends
Cash dividends paid	$ 800	$ 800	$ 1,511	$ 1,506
Cash dividend (in dollars per share)	$ 0.135	$ 0.135
Dividends payable date of record	May 25, 2018	Feb. 23, 2018

Aggregate dividends declared during the period for each share of common stock outstanding.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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- References

No definition available.

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- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

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Namespace Prefix:	us-gaap_
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- Definition

Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

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