Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property and equipment
Property and equipment, gross	$ 120,976	$ 110,086
Less-Accumulated depreciation	(74,115)	(68,670)
Property and equipment, net	46,861	41,416
Depreciation expense	11,400	11,700	11,900
Land
Property and equipment
Property and equipment, gross	2,404	2,404
Transportation equipment
Property and equipment
Property and equipment, gross	46,233	38,352
Transportation equipment | Minimum
Property and equipment
Estimated useful life	1 year
Transportation equipment | Maximum
Property and equipment
Estimated useful life	7 years
Machinery and equipment
Property and equipment
Property and equipment, gross	22,920	21,670
Machinery and equipment | Minimum
Property and equipment
Estimated useful life	1 year
Machinery and equipment | Maximum
Property and equipment
Estimated useful life	15 years
Computer and telephone equipment
Property and equipment
Property and equipment, gross	19,012	18,481
Computer and telephone equipment | Minimum
Property and equipment
Estimated useful life	1 year
Computer and telephone equipment | Maximum
Property and equipment
Estimated useful life	10 years
Buildings and leasehold improvements
Property and equipment
Property and equipment, gross	25,371	24,438
Buildings and leasehold improvements | Minimum
Property and equipment
Estimated useful life	2 years
Buildings and leasehold improvements | Maximum
Property and equipment
Estimated useful life	40 years
Furniture and fixtures
Property and equipment
Property and equipment, gross	$ 5,036	$ 4,741
Furniture and fixtures | Minimum
Property and equipment
Estimated useful life	2 years
Furniture and fixtures | Maximum
Property and equipment
Estimated useful life	17 years