Long-Term Investments - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Investments Schedule [Abstract]
Auction rate securities held, at par value	$ 2,500,000
Maturity of long-term investment	2038
Recognized cumulative losses	$ 400,000
Unrealized gains on auction rate securities	109,000	$ 106,000
Cumulative unrealized gains	400,000
Carrying value of auction rate security	$ 2,217,000		$ 2,052,000
Assumed interest rate	1.16%
Estimated redemption period	5 years
Fair value input discount rate	1.00%
Recognized cumulative losses realized	$ 0