Segment Information - Condensed Balance Sheet Data for Segments (Detail) - USD ($)	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 15,049,059		$ 19,670,613	$ 18,882,602	$ 21,490,586
Accounts receivable, net	9,958,432		9,744,513
Prepaid and other assets	839,755		681,039
Total current assets	25,847,246		30,096,165
Furniture, fixtures and equipment, net	4,477,912		4,919,230
Intangible assets, net	19,285,197		19,474,411
Deferred tax asset, net	11,683,895	$ 11,483,895	12,072,118
Goodwill	54,824,648		54,824,648
Other assets	3,238,422	3,327,633	217,161
Total assets	119,357,320	124,125,982	121,603,733
Current liabilities:
Current portion of debt	0		0
Accrued expenses and other liabilities	4,825,408	4,832,654	4,149,363
Deferred revenue	25,890,104	26,558,707	26,533,983
Total current liabilities	30,715,512		30,683,346
Other long-term liabilities	2,531,017	2,580,952	2,447,037
Total liabilities	33,246,529	33,972,313	33,130,383
Total stockholders' equity	86,110,791	$ 90,153,669	88,473,350
Total liabilities and stockholders' equity	119,357,320		121,603,733
Reis Services [Member]
Current assets:
Accounts receivable, net	9,958,000		9,745,000
Reis Services [Member] | Operating Segments [Member]
Current assets:
Cash and cash equivalents	14,453,000		18,990,000
Accounts receivable, net	9,958,000		9,745,000
Prepaid and other assets	811,000		502,000
Total current assets	25,222,000		29,237,000
Furniture, fixtures and equipment, net	4,478,000		4,919,000
Intangible assets, net	19,285,000		19,474,000
Deferred tax asset, net	285,000		285,000
Goodwill	57,203,000		57,203,000
Other assets	3,238,000		217,000
Total assets	109,711,000		111,335,000
Current liabilities:
Current portion of debt	0		0
Accrued expenses and other liabilities	3,753,000		3,421,000
Deferred revenue	25,890,000		26,534,000
Total current liabilities	29,643,000		29,955,000
Other long-term liabilities	2,531,000		2,447,000
Deferred tax liability, net	36,857,000		34,862,000
Total liabilities	69,031,000		67,264,000
Total stockholders' equity	40,680,000		44,071,000
Total liabilities and stockholders' equity	109,711,000		111,335,000
Other [Member]
Current assets:
Cash and cash equivalents	596,000		681,000
Prepaid and other assets	29,000		179,000
Total current assets	625,000		860,000
Deferred tax asset, net	11,399,000		11,787,000
Goodwill	(2,378,000)		(2,378,000)
Total assets	9,646,000		10,269,000
Current liabilities:
Current portion of debt	0		0
Accrued expenses and other liabilities	1,072,000		729,000
Total current liabilities	1,072,000		729,000
Deferred tax liability, net	(36,857,000)		(34,862,000)
Total liabilities	(35,785,000)		(34,133,000)
Total stockholders' equity	45,431,000		44,402,000
Total liabilities and stockholders' equity	$ 9,646,000		$ 10,269,000