Segment Information - Condensed Operating Data for Segments (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue:
Subscription revenue	$ 11,954,591	$ 11,261,831	$ 34,963,042	$ 34,059,230
Other revenue	137,178	275,344	963,901	1,916,367
Total revenue	12,091,769	11,537,175	35,926,943	35,975,597
Cost of sales	2,944,607	2,925,212	9,527,037	7,881,536
Gross profit	9,147,162	8,611,963	26,399,906	28,094,061
Operating expenses:
Sales and marketing	3,189,695	2,890,739	9,622,811	8,583,395
Product development	1,194,925	1,001,072	3,467,223	3,021,726
General and administrative expenses	3,987,280	3,933,992	11,820,321	11,555,444
Total operating expenses	8,371,900	7,825,803	24,910,355	23,160,565
Other income (expenses):
Interest and other income	979	5,214	2,681	19,380
Interest expense	(32,511)	(28,709)	(97,117)	(78,250)
Total other income (expenses)	(31,532)	(23,495)	(94,436)	(58,870)
Income (loss) before income taxes	743,730	762,665	1,395,115	4,874,626
Reis Services [Member]
Revenue:
Subscription revenue	11,955,000	11,262,000	34,963,000	34,060,000
Other revenue	137,000	276,000	964,000	1,916,000
Total revenue	12,092,000	11,538,000	35,927,000	35,976,000
Cost of sales	2,945,000	2,926,000	9,527,000	7,882,000
Gross profit	9,147,000	8,612,000	26,400,000	28,094,000
Operating expenses:
Sales and marketing	3,190,000	2,890,000	9,623,000	8,583,000
Product development	1,194,000	1,001,000	3,467,000	3,022,000
General and administrative expenses	2,789,000	3,005,000	8,401,000	8,336,000
Total operating expenses	7,173,000	6,896,000	21,491,000	19,941,000
Other income (expenses):
Interest and other income	0	5,000	1,000	19,000
Interest expense	(32,000)	(29,000)	(97,000)	(78,000)
Total other income (expenses)	(32,000)	(24,000)	(96,000)	(59,000)
Income (loss) before income taxes	1,942,000	1,692,000	4,813,000	8,094,000
Other [Member]
Revenue:
Subscription revenue	0	0	0	0
Other revenue	0	0	0	0
Total revenue	0	0	0	0
Cost of sales	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	1,198,000	929,000	3,419,000	3,219,000
Total operating expenses	1,198,000	929,000	3,419,000	3,219,000
Other income (expenses):
Interest and other income	0	0	1,000	0
Interest expense	0	0	0	0
Total other income (expenses)	0	0	1,000	0
Income (loss) before income taxes	$ (1,198,000)	$ (929,000)	$ (3,418,000)	$ (3,219,000)