Intangible Assets - Summary of Identified Intangible Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ (28,764,189)	$ (24,067,250)
Total	15,687,117	16,332,596
Database [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	17,149,000	15,175,000
Accumulated amortization	(13,238,000)	(11,691,000)
Total	3,911,000	3,484,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	14,100,000	14,100,000
Accumulated amortization	(6,417,000)	(5,444,000)
Total	7,683,000	8,656,000
Web Site [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	10,402,000	8,325,000
Accumulated amortization	(7,095,000)	(5,220,000)
Total	3,307,000	3,105,000
Acquired Below Market Lease [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	2,800,000	2,800,000
Accumulated amortization	(2,014,000)	(1,712,000)
Total	$ 786,000	$ 1,088,000