Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets [Abstract]
Trade accounts receivable-billed, allowance	$ 3,147	$ 2,421
Property and equipment, accumulated depreciation	120,643	116,125
Software, accumulated amortization	68,513	56,521
Client contracts, accumulated amortization	184,763	159,225
Long-term debt, unamortized original issue discount	$ 25,302	$ 30,256
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000	10,000
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	100,000
Common stock, shares reserved for employee stock purchase plan and stock incentive plans	6,904	8,676
Common stock, shares outstanding	33,734	33,822
Treasury stock, shares	31,530	30,707