Property and Equipment (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of property and equipment
Property and equipment, at cost	$ 171,452	$ 165,998
Accumulated depreciation	(102,124)	(92,855)
Property and equipment, net	69,328	73,143
Depreciation	13,211	14,764	13,525
Leasehold improvements
Summary of property and equipment
Property and equipment, at cost	19,610	19,345
Leasehold improvements | Minimum
Summary of property and equipment
Estimated useful lives	1 year
Leasehold improvements | Maximum
Summary of property and equipment
Estimated useful lives	15 years
Furniture and fixtures
Summary of property and equipment
Property and equipment, at cost	30,670	30,590
Furniture and fixtures | Minimum
Summary of property and equipment
Estimated useful lives	3 years
Furniture and fixtures | Maximum
Summary of property and equipment
Estimated useful lives	10 years
Equipment
Summary of property and equipment
Property and equipment, at cost	19,660	18,482
Equipment | Minimum
Summary of property and equipment
Estimated useful lives	3 years
Equipment | Maximum
Summary of property and equipment
Estimated useful lives	26 years
Computer software
Summary of property and equipment
Property and equipment, at cost	74,081	72,184
Computer software | Minimum
Summary of property and equipment
Estimated useful lives	1 year
Computer software | Maximum
Summary of property and equipment
Estimated useful lives	10 years
Data processing equipment
Summary of property and equipment
Property and equipment, at cost	20,207	19,692
Data processing equipment | Minimum
Summary of property and equipment
Estimated useful lives	2 years
Data processing equipment | Maximum
Summary of property and equipment
Estimated useful lives	5 years
Property and equipment under capital leases
Summary of property and equipment
Property and equipment, at cost	1,900	1,800
Accumulated depreciation	800	1,000
Buildings
Summary of property and equipment
Property and equipment, at cost	5,284	3,765
Buildings | Minimum
Summary of property and equipment
Estimated useful lives	10 years
Buildings | Maximum
Summary of property and equipment
Estimated useful lives	30 years
Land
Summary of property and equipment
Property and equipment, at cost	$ 1,940	$ 1,940