Segment Information - Condensed Operating Data for Segments (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Subscription revenue	$ 14,206,000	$ 12,137,000	$ 13,416,000	$ 11,131,000	$ 10,726,000	$ 10,469,000	$ 10,194,000	$ 9,946,000	$ 50,890,438	$ 41,335,155	$ 34,721,088
Cost of sales of subscription revenue									9,081,624	8,037,019	6,973,772
Gross profit									41,808,814	33,298,136	27,747,316
Operating expenses:
Sales and marketing									11,700,840	10,235,349	8,349,544
Product development									3,711,054	3,472,875	3,121,729
General and administrative expenses									14,267,027	12,040,343	11,909,462
Total operating expenses									29,678,921	25,748,567	23,380,735
Other income (expenses):
Interest and other income									37,857	22,016	9,981
Interest expense									(91,767)	(113,200)	(113,200)
Total other income (expenses)									(53,910)	(91,184)	(103,219)
Income (loss) before income taxes and discontinued operations									12,075,983	7,458,385	4,263,362
Income (loss) from discontinued operations, before income taxes									3,643,000	(951,000)	(566,000)
Reis Services [Member]
Segment Reporting Information [Line Items]
Subscription revenue									50,890,000	41,335,000	34,721,000
Cost of sales of subscription revenue									9,081,000	8,037,000	6,974,000
Gross profit									41,809,000	33,298,000	27,747,000
Operating expenses:
Sales and marketing									11,701,000	10,235,000	8,350,000
Product development									3,711,000	3,473,000	3,122,000
General and administrative expenses									9,892,000	7,940,000	6,989,000
Total operating expenses									25,304,000	21,648,000	18,461,000
Other income (expenses):
Interest and other income									38,000	22,000	10,000
Interest expense									(92,000)	(113,000)	(113,000)
Total other income (expenses)									(54,000)	(91,000)	(103,000)
Income (loss) before income taxes and discontinued operations									16,451,000	11,559,000	9,183,000
Income (loss) from discontinued operations, before income taxes									0	0	0
Other [Member]
Segment Reporting Information [Line Items]
Subscription revenue									0	0	0
Cost of sales of subscription revenue									0	0	0
Gross profit									0	0	0
Operating expenses:
Sales and marketing									0	0	0
Product development									0	0	0
General and administrative expenses									4,375,000	4,101,000	4,920,000
Total operating expenses									4,375,000	4,101,000	4,920,000
Other income (expenses):
Interest and other income									0	0	0
Interest expense									0	0	0
Total other income (expenses)									0	0	0
Income (loss) before income taxes and discontinued operations									(4,375,000)	(4,101,000)	(4,920,000)
Income (loss) from discontinued operations, before income taxes									3,651,000	(920,000)	(557,000)
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Subscription revenue									0	0	0
Cost of sales of subscription revenue									0	0	0
Gross profit									0	0	0
Operating expenses:
Sales and marketing									0	0	0
Product development									0	0	0
General and administrative expenses									0	0	0
Total operating expenses									0	0	0
Other income (expenses):
Interest and other income									0	0	0
Interest expense									0	0	0
Total other income (expenses)									0	0	0
Income (loss) before income taxes and discontinued operations									0	0	0
Income (loss) from discontinued operations, before income taxes									$ (8,000)	$ (31,000)	$ (9,000)