Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets	$ 1,696,000	$ 1,434,000	$ 3,368,216	$ 2,811,949
Database [Member]
Finite-Lived Intangible Assets [Line Items]
Amount capitalized to intangible asset	1,529,000	1,390,000	2,777,000	2,721,000
Amortization expense for intangible assets	917,000	658,000	1,789,000	1,270,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets	231,000	234,000	462,000	469,000
Website [Member]
Finite-Lived Intangible Assets [Line Items]
Amount capitalized to intangible asset	871,000	732,000	1,751,000	1,390,000
Amortization expense for intangible assets	$ 548,000	466,000	$ 1,118,000	922,000
Acquired Below Market Lease [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization expense for intangible assets		$ 76,000		$ 151,000