Summary of Significant Accounting Policies - Cost and Carrying Value of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Cost	$ 136,902	$ 124,249
Accumulated Depreciation and Amortization	(75,022)	(63,835)
Carrying Value	61,880	60,414
Sales facilities
Property, Plant and Equipment [Line Items]
Cost	71,870	60,964
Accumulated Depreciation and Amortization	(34,272)	(25,802)
Carrying Value	37,598	35,162
Airplane
Property, Plant and Equipment [Line Items]
Cost	31,230	31,230
Accumulated Depreciation and Amortization	(10,813)	(10,145)
Carrying Value	20,417	21,085
Computer software and equipment
Property, Plant and Equipment [Line Items]
Cost	23,801	22,660
Accumulated Depreciation and Amortization	(21,997)	(20,730)
Carrying Value	1,804	1,930
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost	7,640	7,339
Accumulated Depreciation and Amortization	(6,357)	(5,817)
Carrying Value	1,283	1,522
Other
Property, Plant and Equipment [Line Items]
Cost	2,361	2,056
Accumulated Depreciation and Amortization	(1,583)	(1,341)
Carrying Value	$ 778	$ 715