Investments - Summary of Operating and Balance Sheet Data (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Income Statement [Abstract]
Expenses	$ 6,284	$ 4,188
Income tax (expense) benefit	478	(67)
Net increase in net assets resulting from operations	15,119	16,400
Lawn Doctor, Inc.
Income Statement [Abstract]
Revenues	9,664	8,794
Expenses	8,868	7,978
Income (loss) before taxes	796	816
Income tax (expense) benefit	203	224
Consolidated net income (loss)	593	592
Net loss attributable to non-controlling interests	39	75
Net increase in net assets resulting from operations	632	667
Balance Sheet Related Disclosures [Abstract]
Current assets	12,135		$ 13,926
Non-current assets	91,009		92,309
Current liabilities	9,592		7,961
Non-current liabilities	63,818		63,576
Non-controlling interests	(539)		(500)
Stockholders’ equity	$ 30,273		$ 35,198
Ownership percentage	61.00%		61.00%
Polyform Products, Co.
Income Statement [Abstract]
Revenues	$ 5,823	6,793
Expenses	5,391	5,312
Income (loss) before taxes	432	1,481
Income tax (expense) benefit	124	423
Consolidated net income (loss)	308	1,058
Net loss attributable to non-controlling interests	0	0
Net increase in net assets resulting from operations	308	1,058
Balance Sheet Related Disclosures [Abstract]
Current assets	10,333		$ 9,940
Non-current assets	28,584		28,948
Current liabilities	2,136		2,290
Non-current liabilities	21,548		21,557
Non-controlling interests	0		0
Stockholders’ equity	$ 15,233		$ 15,041
Ownership percentage	87.00%		87.00%
Roundtables
Income Statement [Abstract]
Revenues	$ 3,543	2,852
Expenses	3,724	2,971
Income (loss) before taxes	(181)	(119)
Income tax (expense) benefit	(43)	(26)
Consolidated net income (loss)	(138)	(93)
Net loss attributable to non-controlling interests	0	0
Net increase in net assets resulting from operations	(138)	(93)
Balance Sheet Related Disclosures [Abstract]
Current assets	10,759		$ 2,043
Non-current assets	61,307		61,955
Current liabilities	13,374		4,738
Non-current liabilities	19,786		19,771
Non-controlling interests	0		0
Stockholders’ equity	$ 38,906		$ 39,489
Ownership percentage	81.00%		81.00%
HSH
Income Statement [Abstract]
Revenues	$ 9,606	7,963
Expenses	8,767	7,535
Income (loss) before taxes	839	428
Income tax (expense) benefit	185	94
Consolidated net income (loss)	654	334
Net loss attributable to non-controlling interests	0	0
Net increase in net assets resulting from operations	654	$ 334
Balance Sheet Related Disclosures [Abstract]
Current assets	14,354		$ 14,260
Non-current assets	38,697		39,653
Current liabilities	6,715		7,341
Non-current liabilities	28,481		28,536
Non-controlling interests	0		0
Stockholders’ equity	$ 17,855		$ 18,036
Ownership percentage	75.00%		75.00%
ATA
Income Statement [Abstract]
Revenues	$ 14,158
Expenses	15,574
Income (loss) before taxes	(1,416)
Income tax (expense) benefit	0
Consolidated net income (loss)	(1,416)
Net loss attributable to non-controlling interests	0
Net increase in net assets resulting from operations	(1,416)
Balance Sheet Related Disclosures [Abstract]
Current assets	5,571		$ 10,029
Non-current assets	90,606		90,510
Current liabilities	5,806		9,002
Non-current liabilities	43,458		43,458
Non-controlling interests	0		0
Stockholders’ equity	$ 46,913		$ 48,079
Ownership percentage	75.00%		75.00%
Douglas
Income Statement [Abstract]
Revenues	$ 5,399
Expenses	5,824
Income (loss) before taxes	(425)
Income tax (expense) benefit	(104)
Consolidated net income (loss)	(321)
Net loss attributable to non-controlling interests	0
Net increase in net assets resulting from operations	(321)
Balance Sheet Related Disclosures [Abstract]
Current assets	13,684		$ 13,177
Non-current assets	35,528		40,311
Current liabilities	5,210		4,159
Non-current liabilities	15,711		15,711
Non-controlling interests	0		0
Stockholders’ equity	$ 28,291		$ 33,618
Ownership percentage	90.00%		90.00%
Clarion
Income Statement [Abstract]
Revenues	$ 3,619
Expenses	2,833
Income (loss) before taxes	786
Income tax (expense) benefit	228
Consolidated net income (loss)	558
Net loss attributable to non-controlling interests	0
Net increase in net assets resulting from operations	558
Balance Sheet Related Disclosures [Abstract]
Current assets	3,628		$ 3,084
Non-current assets	65,710		66,182
Current liabilities	372		420
Non-current liabilities	22,500		22,500
Non-controlling interests	0		0
Stockholders’ equity	$ 46,466		$ 46,346
Ownership percentage	99.00%		99.00%