Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Trade accounts receivable-billed, allowance	$ 2,421	$ 1,837
Property and equipment, accumulated depreciation	116,125	94,236
Software, accumulated amortization	56,521	45,579
Client contracts, accumulated amortization	159,225	133,218
Current maturities of long-term debt, unamortized original issue discount	0	621
Long-term debt, unamortized original issue discount	$ 30,256	$ 34,841
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	8,675,558	5,892,315
Common stock, shares outstanding	33,822,232	34,120,789
Treasury stock, shares	30,551,519	29,956,808