Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary of property and equipment
Property and equipment, at cost	$ 170,064	$ 157,350
Accumulated depreciation	(96,036)	(86,102)
Property and equipment, net	74,028	71,248
Depreciation expense	15,235	14,030	13,653
Leasehold improvements
Summary of property and equipment
Property and equipment, at cost	19,678	19,827
Estimated useful lives, low end of range (in years)	1
Estimated useful lives, high end of range (in years)	15
Furniture and fixtures
Summary of property and equipment
Property and equipment, at cost	31,840	30,137
Estimated useful lives, low end of range (in years)	3
Estimated useful lives, high end of range (in years)	10
Equipment
Summary of property and equipment
Property and equipment, at cost	18,864	17,366
Estimated useful lives, low end of range (in years)	3
Estimated useful lives, high end of range (in years)	26
Computer software
Summary of property and equipment
Property and equipment, at cost	72,799	67,830
Estimated useful lives, low end of range (in years)	5
Estimated useful lives, high end of range (in years)	10
Data processing equipment
Summary of property and equipment
Property and equipment, at cost	21,178	22,190
Estimated useful lives, low end of range (in years)	5
Estimated useful lives, high end of range (in years)	10
Property and equipment under capital leases
Summary of property and equipment
Property and equipment, at cost	1,800	1,800
Accumulated depreciation	(1,000)	(1,000)
Buildings
Summary of property and equipment
Property and equipment, at cost	3,765
Estimated useful lives, low end of range (in years)	10
Estimated useful lives, high end of range (in years)	30
Land
Summary of property and equipment
Property and equipment, at cost	$ 1,940