Investments - Equity Securities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Equity Securities, FV-NI, Gain (Loss) [Abstract]
Cost	$ 4,111
Gross Gains	8
Gross Losses	(71)
Fair Value	4,048
Unrealized Gain (Loss) on Equity Securities [Abstract]
Cost		$ 7,223
Gross Gains		39
Gross Losses		(16)
Fair Value		$ 7,246
Recognized net losses on equity securities still held	$ 100