Segment Information - Additional Information (Detail)	1 Months Ended	6 Months Ended
	Jul. 31, 2017 USD ($)	Jun. 30, 2017 Subscriber	Jun. 30, 2016
Subsequent Event [Member]
Segment Reporting Information [Line Items]
Payments received against accounts receivable | $	$ 4,711,000
Percentage collected from trade accounts receivable	49.20%
Reis Services [Member]
Segment Reporting Information [Line Items]
Percentage of Reis Service's revenue by major customer		3.30%	8.10%
Number of subscribers contributing largest share among accounts receivable | Subscriber		17
Aggregate percentage of subscribers contributing largest share among accounts receivable		55.70%
Percentage of Reis Service's accounts receivable by major subscriber		12.10%
Percentage of deferred revenue by major subscriber		4.70%