Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset measured and recognized at fair value on recurring basis	$ 0		$ 0		$ 0
Impairment of goodwill		$ 1,000,000		$ 988,000
Liability measured and recognized at fair value on non-recurring basis	0		0		0
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalent at recurring basis	0		0		0
Fair Value Measurements, Non-recurring | Fair Value, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Privately-held investments measured at fair value	300,000		300,000		$ 300,000
Impairment of privately-held investments	$ 0		$ 0