Condensed Consolidated Statements of Equity (Unaudited) - USD ($)		Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]		Total
Balance (in shares) at Mar. 31, 2017		2,042,789
Balance at Mar. 31, 2017		$ 510,696	$ 4,205,536	$ 18,461,347	$ (212,047)	$ (803,138)		$ 22,162,394
Net income	[1]			968,389		18,239		986,628
Loss on marketable securities, net of tax					(94,997)			(94,997)
Foreign currency translation gain					135,634	(845)		134,789
Redeemable non-controlling interest			(25,000)					(25,000)
Balance (in shares) at Jun. 30, 2017		2,042,789
Balance at Jun. 30, 2017		$ 510,696	4,180,536	19,429,736	(171,410)	(785,744)		23,163,814
Balance (in shares) at Mar. 31, 2017		2,042,789
Balance at Mar. 31, 2017		$ 510,696	4,205,536	18,461,347	(212,047)	(803,138)		22,162,394
Foreign currency translation gain								255,433
Balance (in shares) at Dec. 31, 2017		2,042,789
Unrealized gain (loss) on interest rate swaps, net of tax
Balance at Dec. 31, 2017		$ 510,696	4,163,436	19,137,023	117,580	(782,699)		23,146,036
Balance (in shares) at Jun. 30, 2017		2,042,789
Balance at Jun. 30, 2017		$ 510,696	4,180,536	19,429,736	(171,410)	(785,744)		23,163,814
Net income				421,701		(18,556)		403,145
Loss on marketable securities, net of tax					(284,483)			(284,483)
Foreign currency translation gain					74,694	23,883		98,577
Redeemable non-controlling interest			(8,550)					(8,550)
Balance (in shares) at Sep. 30, 2017		2,042,789
Balance at Sep. 30, 2017		$ 510,696	4,171,986	19,851,437	(381,199)	(780,417)		23,372,503
Net income				(671,939)		16,514		(655,425)
Loss on marketable securities, net of tax					415,441			415,441
Foreign currency translation gain					40,863	(18,796)		22,067
Redeemable non-controlling interest			(8,550)					(8,550)
Reclassification due to the Tax Cuts and Jobs Act				(42,475)	42,475
Balance (in shares) at Dec. 31, 2017		2,042,789
Unrealized gain (loss) on interest rate swaps, net of tax
Balance at Dec. 31, 2017		$ 510,696	4,163,436	19,137,023	117,580	(782,699)		23,146,036
Balance (in shares) at Mar. 31, 2018		2,043,607
Balance at Mar. 31, 2018		$ 510,901	4,171,869	20,695,981	(260,900)	(874,767)	[1]	24,243,084
Net income	[1]			2,828,694		(46,259)		2,782,435
Foreign currency translation gain					30,508	17,152	[1]	47,660
Balance (in shares) at Jun. 30, 2018		2,043,607
Adoption of ASU 2016-01				(106,341)	106,341		[1]
Balance at Jun. 30, 2018		$ 510,901	4,171,869	23,418,334	(124,051)	(903,874)	[1]	27,073,179
Balance (in shares) at Mar. 31, 2018		2,043,607
Balance at Mar. 31, 2018		$ 510,901	4,171,869	20,695,981	(260,900)	(874,767)	[1]	24,243,084
Foreign currency translation gain								200,346
Balance (in shares) at Dec. 31, 2018		2,024,331
Unrealized gain (loss) on interest rate swaps, net of tax								(134,327)
Balance at Dec. 31, 2018		$ 506,084	4,195,484	18,694,300	(120,284)	(958,216)	[1]	22,317,368
Balance (in shares) at Jun. 30, 2018		2,043,607
Balance at Jun. 30, 2018		$ 510,901	4,171,869	23,418,334	(124,051)	(903,874)	[1]	27,073,179
Net income				(1,321,185)		(42,190)	[1]	(1,363,375)
Foreign currency translation gain					24,250	7,964	[1]	32,214
Balance (in shares) at Sep. 30, 2018		2,044,614
Exercise of stock options (in shares)		1,682
Exercise of stock options		$ 421	17,341				[1]	17,762
Repurchase of common stock (in shares)		(675)
Repurchase of common stock		$ (170)	(1,377)	(21,212)			[1]	(22,759)
Unrealized gain (loss) on interest rate swaps, net of tax					29,124		[1]	29,124
Balance at Sep. 30, 2018		511,152	4,187,833	22,075,937	(70,677)	(938,100)	[1]	25,766,145
Net income	[1]			(2,714,951)		(26,749)		(2,741,700)
Foreign currency translation gain					113,843	6,633	[1]	120,476
Balance (in shares) at Dec. 31, 2018		2,024,331
Repurchase of common stock (in shares)		(20,283)
Repurchase of common stock		$ (5,068)	1,377	(666,686)			[1]	(670,377)
Unrealized gain (loss) on interest rate swaps, net of tax					(163,450)		[1]	(163,451)
Equity-based compensation			6,274				[1]	6,274
Balance at Dec. 31, 2018		$ 506,084	$ 4,195,484	$ 18,694,300	$ (120,284)	$ (958,216)	[1]	$ 22,317,368

[1] Excludes amount attributable to redeemable non-controlling interest in Contrail Aviation.