Financial Instruments - Credit Losses (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Expected loss rate		40.90%
Due from Employees	$ 44,114,000	$ 44,114,000	$ 43,670,000
2020	0	0
2019	555,000	555,000
2018	186,000	186,000
2017	762,000	762,000
2016	875,000	875,000
2015 and prior	2,931,000	2,931,000
Total	5,309,000	5,309,000
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,908,000	3,673,000
Additions and other adjustments	(5,000)	230,000
Ending balance	3,903,000	3,903,000	$ 3,673,000
Minimum [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Service Period			3 years
Maximum [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Service Period			10 years
Notes Receivable, Five Years and Older [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	2,900,000	2,900,000
Notes Receivable, Under Five Years [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	$ 972,000	$ 972,000