PROPERTY AND EQUIPMENT (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and Equipment
Property and equipment, gross	$ 115,271,000	$ 108,364,000
Less: Accumulated depreciation	(88,298,000)	(75,686,000)
Property and equipment, net	26,973,000	32,678,000
Depreciation expense	27,725,000	22,025,000	$ 22,864,000
Impairment of property, plant and equipment	0
Computer and office equipment
Property and Equipment
Property and equipment, gross	31,371,000	30,060,000
Software capitalized for internal use
Property and Equipment
Property and equipment, gross	17,470,000	16,481,000
Vehicles
Property and Equipment
Property and equipment, gross	2,379,000	2,552,000
Medical equipment
Property and Equipment
Property and equipment, gross	36,230,000	32,086,000
Work in progress
Property and Equipment
Property and equipment, gross	2,478,000	4,370,000
Furniture and fixtures
Property and Equipment
Property and equipment, gross	5,534,000	5,319,000
Leasehold improvements
Property and Equipment
Property and equipment, gross	19,809,000	17,496,000
Assets held under capital leases
Property and Equipment
Depreciation expense	$ 15,900,000	$ 15,800,000	$ 17,700,000