Long-Term Debt and Financing Arrangements - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2011 Chassis
Line Of Credit Facility [Line Items]
Maximum unsecured borrowing capacity				$ 50,000,000
Line of credit, expiration date			Dec. 31, 2018
Number of chassis leased | Chassis					3,126
Chassis, lease agreement period (years)					10 years
Capital lease interest paid	$ 600,000	$ 700,000	$ 800,000
Standby Letters of Credit [Member]
Line Of Credit Facility [Line Items]
Outstanding letters of credit	$ 11,800,000
Letters of credit expiration, years	2017
Revolving Line of Credit Facility [Member] | Bank Revolving Line of Credit [Member]
Line Of Credit Facility [Line Items]
Unused and available borrowings under bank revolving line of credit	$ 38,200,000	$ 41,800,000
Minimum [Member]
Line Of Credit Facility [Line Items]
Commitment fee charged on the unused line of credit				0.10%
Interest coverage ratio				2.00%
Maximum [Member]
Line Of Credit Facility [Line Items]
Commitment fee charged on the unused line of credit				0.25%
Total leverage ratio				3.00%
LIBOR rate [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Interest rate under the Credit Agreement				1.00%
LIBOR rate [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Interest rate under the Credit Agreement				1.75%
Prime Rate [Member]
Line Of Credit Facility [Line Items]
Interest rate under the Credit Agreement				0.75%