Quarterly Results of Operations (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Gross revenues
Revenues	$ 75,318,000	$ 71,856,000	$ 69,197,000	$ 61,800,000	$ 72,167,000	$ 85,359,000	$ 86,965,000	$ 75,479,000	$ 278,171,000	$ 319,970,000
Net income	1,050,000	1,390,000	1,085,000	831,000	1,128,000	944,000	905,000	661,000	4,356,000	3,638,000
Basic net income per share	$ 0.03	$ 0.04	$ 0.03	$ 0.03	$ 0.03	$ 0.03	$ 0.03	$ 0.02	$ 0.13	$ 0.11
Diluted net income per share	$ 0.03	$ 0.04	$ 0.03	$ 0.02	$ 0.02	$ 0.03	$ 0.03	$ 0.02	$ 0.12	$ 0.10
Transportation services
Gross revenues
Revenues	75,072,000	70,596,000	69,033,000	61,497,000	71,436,000	85,262,000	86,438,000	74,944,000	276,198,000	318,080,000
Net income									4,062,000	2,991,000
Agent support services
Gross revenues
Revenues	246,000	1,260,000	164,000	303,000	731,000	97,000	527,000	535,000	1,973,000	1,890,000
Net income									$ 294,000	$ 647,000