CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Trade accounts receivable-billed, allowance	$ 3,628	$ 3,735
Property and equipment, accumulated depreciation	105,073	98,029
Intangibles, accumulated amortization	139,836	125,437
Customer contract costs, accumulated amortization	39,893	31,526
Long-term debt, unamortized discounts	$ 5,346	$ 10,053
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	5,929,000	3,661,000
Common stock, shares outstanding	32,713,000	32,891,000
Treasury stock, shares	35,980,000	35,356,000
Software
Intangibles, accumulated amortization	$ 139,836	$ 125,437
Acquired customer contracts
Intangibles, accumulated amortization	$ 105,778	$ 93,767