Segment Information - Condensed Operating Data for Segments (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Subscription revenue	$ 11,537,175	$ 12,137,228	$ 35,975,597	$ 36,684,041
Cost of sales of subscription revenue	2,925,212	2,363,635	7,881,536	6,683,601
Gross profit	8,611,963	9,773,593	28,094,061	30,000,440
Operating expenses:
Sales and marketing	2,890,739	2,804,498	8,583,395	8,918,285
Product development	1,001,072	925,673	3,021,726	2,678,114
General and administrative expenses	3,933,992	3,598,697	11,555,444	10,301,919
Total operating expenses	7,825,803	7,328,868	23,160,565	21,898,318
Other income (expenses):
Interest and other income	5,214	11,300	19,380	26,894
Interest expense	(28,709)	(28,352)	(78,250)	(84,848)
Total other income (expenses)	(23,495)	(17,052)	(58,870)	(57,954)
Income (loss) before income taxes and discontinued operations	762,665	2,427,673	4,874,626	8,044,168
Income from discontinued operations, before income taxes	0	226,000	0	2,001,000
Reis Services [Member]
Segment Reporting Information [Line Items]
Subscription revenue	11,538,000	12,137,000	35,976,000	36,684,000
Cost of sales of subscription revenue	2,926,000	2,364,000	7,882,000	6,684,000
Gross profit	8,612,000	9,773,000	28,094,000	30,000,000
Operating expenses:
Sales and marketing	2,890,000	2,804,000	8,583,000	8,918,000
Product development	1,001,000	926,000	3,022,000	2,678,000
General and administrative expenses	3,005,000	2,528,000	8,336,000	6,912,000
Total operating expenses	6,896,000	6,258,000	19,941,000	18,508,000
Other income (expenses):
Interest and other income	5,000	11,000	19,000	26,000
Interest expense	(29,000)	(28,000)	(78,000)	(84,000)
Total other income (expenses)	(24,000)	(17,000)	(59,000)	(58,000)
Income (loss) before income taxes and discontinued operations	1,692,000	3,498,000	8,094,000	11,434,000
Income from discontinued operations, before income taxes	0	0	0	0
Other [Member]
Segment Reporting Information [Line Items]
Subscription revenue	0	0	0	0
Cost of sales of subscription revenue	0	0	0	0
Gross profit	0	0	0	0
Operating expenses:
Sales and marketing	0	0	0	0
Product development	0	0	0	0
General and administrative expenses	929,000	1,070,000	3,219,000	3,390,000
Total operating expenses	929,000	1,070,000	3,219,000	3,390,000
Other income (expenses):
Interest and other income	0	0	0	0
Interest expense	0	0	0	0
Total other income (expenses)	0	0	0	0
Income (loss) before income taxes and discontinued operations	(929,000)	(1,070,000)	(3,219,000)	(3,390,000)
Income from discontinued operations, before income taxes	$ 0	$ 226,000	$ 0	$ 2,001,000