CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Trade accounts receivable-billed, allowance	$ 3,600	$ 3,323
Property and equipment, accumulated depreciation	112,282	138,065
Current maturities of long-term debt, unamortized original issue discount	7,923	0
Long-term debt, unamortized original issue discount	$ 0	$ 14,169
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares reserved for employee stock purchase plan and stock incentive plans	4,664,000	6,032,000
Common stock warrants, issued	2,851,000	2,851,000
Common stock, shares outstanding	32,555,000	33,945,000
Common stock warrants, outstanding	2,851,000	2,851,000
Treasury stock, shares	34,601,000	32,763,000
Software
Accumulated amortization	$ 95,094	$ 86,797
Client contracts
Accumulated amortization	$ 87,890	$ 88,585