Line items represent reporting 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.

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Investments Other investments (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2014	Mar. 31, 2014
Investment [Line Items]
Other Investments				$ 2,079	$ 3,721
Performance Share Grant Agreement [Member]
Investment [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance						475,000
Minimum [Member]
Investment [Line Items]
Share Price						$ 10.00
Maximum [Member]
Investment [Line Items]
Share Price						$ 18.00	$ 18.00
Clause 1, 2 and 3 [Member]
Investment [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance						350,000	375,000
Clause 2 [Member]
Investment [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance						125,000	125,000
Share Price						$ 12.00	$ 15.00
Clause 3 [Member]
Investment [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance							125,000
Share Price						$ 15.00
Clause 1 and 2 [Member]
Investment [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance						225,000	250,000
Management [Member]
Investment [Line Items]
Sale of Stock, Consideration Received on Transaction	$ 1,000		$ 300
Effect on Future Cash Flows, Amount		$ 1,000
Proceeds from Sale of Debt Securities, Available-for-sale				$ 1,300