Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of property and equipment
Property and equipment, at cost	$ 202,698	$ 206,361
Accumulated depreciation	(139,269)	(118,694)
Property and equipment, net	63,429	87,667
Depreciation	25,649	20,983	$ 18,358
Leasehold improvements
Summary of property and equipment
Property and equipment, at cost	$ 21,790	22,106
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	$ 28,482	30,529
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	$ 20,248	20,802
Equipment | Minimum
Summary of property and equipment
Estimated useful lives	2 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	$ 100,507	99,644
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	$ 17,056	18,678
Data processing equipment | Minimum
Summary of property and equipment
Estimated useful lives	1 year
Data processing equipment | Maximum
Summary of property and equipment
Estimated useful lives	5 years
Buildings
Summary of property and equipment
Property and equipment, at cost	$ 11,772	11,759
Buildings | Minimum
Summary of property and equipment
Estimated useful lives	1 year
Buildings | Maximum
Summary of property and equipment
Estimated useful lives	30 years
Land
Summary of property and equipment
Property and equipment, at cost	$ 2,843	2,843
Property and equipment under capital leases
Summary of property and equipment
Property and equipment, at cost	1,600	1,900
Accumulated depreciation	$ (1,100)	$ (1,000)