Investments (Details-1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Equity Securities [Abstract]
Equity Securities	$ 14,546	$ 9,363
Equity method investments:
Equity method investments	71,648	66,339	$ 20,400
Other Investments	2,298	2,298
Total investments	88,492	78,000
Results of Investment Liquidation [Abstract]
Proceeds from sale of investments	216	960	677
Gain (loss) on sale of investments	580	476	522
ATC and ATC Holdco [Member]
Equity method investments:
Equity method investments	71,609	66,313
Other Equity Method Investments [Member]
Equity method investments:
Equity method investments	39	26
MGE [Member]
Equity Securities [Abstract]
Equity Securities	209	388
Equity method investments:
Equity method investments	0	0
Other Investments	0	0
Total investments	209	388
Results of Investment Liquidation [Abstract]
Proceeds from sale of investments	2	3	0
Gain (loss) on sale of investments	(343)	3	$ 0
MGE [Member] | ATC and ATC Holdco [Member]
Equity method investments:
Equity method investments	0	0
MGE [Member] | Other Equity Method Investments [Member]
Equity method investments:
Equity method investments	$ 0	$ 0