Summary of Significant Accounting Principles (Details-1) - USD ($)	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	$ 69,913,000	$ 83,102,000
Restricted cash	605,000	634,000
Receivable - margin account	1,304,000	1,193,000
Cash, cash equivalents, and restricted cash	71,822,000	84,929,000	$ 100,267,000	$ 112,094,000
MGE [Member]
Cash Cash Equivalents And Restricted Cash [Line Items]
Cash and cash equivalents	6,383,000	4,843,000
Restricted cash	605,000	634,000
Receivable - margin account	1,304,000	1,193,000
Cash, cash equivalents, and restricted cash	$ 8,292,000	$ 6,670,000	$ 7,816,000	$ 10,093,000