Financial Instruments - Credit Losses (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Expected loss rate	40.90%
Due from Employees	$ 44,960,000	$ 43,670,000
2020	0
2019	555,000
2018	186,000
2017	769,000
2016	875,000
2015 and prior	2,933,000
Total	5,318,000
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance, January 1, 2020 upon adoption of ASU 2016-13	3,673,000
Additions	235,000
Ending balance, March 31, 2020	3,908,000	$ 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, March 31, 2020	2,900,000
Notes Receivable, Under Five Years [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance, March 31, 2020	$ 975,000