Balance Sheets - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Cash and equivalents	$ 14,997,613	$ 23,095,977	$ 17,436,627
Marketable securities	421,554,499	268,638,359	306,086,429
Trade receivables, net of reserve	36,575,028	36,760,812	50,522,946
Contract assets, prepaid and other	14,223,037	12,077,935	12,376,569
Current assets	487,350,177	340,573,083	386,422,571
Computer equipment	13,339,425	13,979,609	14,463,275
Furniture and fixtures	76,135,675	92,804,040	83,719,079
Buildings	190,105,517	240,288,774	250,962,956
Land	26,717,577	40,959,230	43,163,211
Accumulated depreciation	138,527,057	175,832,443	178,192,159
Fixed assets	167,771,137	212,199,210	214,116,362
Other assets	7,193,998	8,430,515	9,466,338
Deferred tax assets	7,160,037	8,257,144	9,223,246
Total assets	669,475,349	569,459,952	619,228,517
Accounts payable	211,391	701,524	227,663
Taxes payable	3,111,878	1,825,528	3,882,391
Accrued expenses	24,327,709	23,916,832	22,831,337
Deferred revenue	39,711,207	52,666,651	57,619,181
Current liabilities	67,362,185	79,110,535	84,560,572
Deferred tax liabilities	26,951,474	12,409,407	19,154,929
Tax reserves	17,411,282	17,039,282	18,584,766
Total liabilities	111,724,941	108,559,224	122,300,267
Common stock value	37,190,854	37,190,854	37,190,854
Additional paid-in capital	122,907,959	122,907,959	122,907,959
Retained income	397,651,595	300,801,915	289,634,133
Unrealized after-tax security gains	0	0	47,195,304
Shareholder equity	557,750,408	460,900,728	496,928,250
Total liabilities and shareholder equity	$ 669,475,349	$ 569,459,952	$ 619,228,517