Investment And Other Gains Investment And Other Gains (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Marketable Securities, Realized Gain (Loss)	$ 0	$ 0	$ 0	$ 10,038
Proceeds from sales of marketable securities			$ 0	18,182	$ 18,182
2017 Sales Transaction [Member]
Proceeds from sales of marketable securities				$ 11,718
Marketable securities						$ 11,745
Available-for-sale Securities, Amortized Cost Basis						$ 1,680
2016 Sales Transaction [Member]
Proceeds from sales of marketable securities					$ 6,464