Description of Business and Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Customer Segment shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 shares
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Maturity period of highly liquid investments to be considered as cash equivalents	three months or less
Impairment on long-lived assets | $	$ 0
Amortization of Deferred Revenue | $	$ 399,000	$ 1,080,000
Number of major customers | Customer	10
Options outstanding for the purchase of common stock	65,437	63,285	67,082
Number of shares relating to options included in the calculation of diluted earnings per share	8,133	11,445
Preferred stock convertible into common stock at rate of shares of common stock	64,000	64,000
Number of reporting segment | Segment	1
Minimum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Percentage of Reimbursement of cost incurred	65.00%
Minimum [Member] | Freight Operating Revenues [Member] | Customer Concentration Risk [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Company's freight operating revenue by customer	10.00%	10.00%
Maximum [Member]
Description Of Business And Summary Of Significant Accounting Policies [Line Items]
Percentage of Reimbursement of cost incurred	100.00%