Investments Real estate investments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, All Other Investments [Abstract]
Real estate investments, at fair value (cost of $10,225 and 10,225, respectively)	$ 10,662	$ 10,662	$ 10,662

Amount of real estate owned for income production and capital accretion potential, not otherwise specified in the existing taxonomy. Such real estate excludes that which is occupied or used in the business, for entertainment purposes, or held in inventory for specific purposes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_RealEstateInvestmentsOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant