Property, Equipment and Software, net (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, equipment and software, at cost	$ 57,280	$ 58,539
Less accumulated depreciation and amortization	(40,580)	(34,967)
Property, equipment and software, net	$ 16,700	23,572
Computer/office equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life	36 months
Property, equipment and software, at cost	$ 15,107	15,419
Capitalized internal-use software
Property, Plant and Equipment [Line Items]
Estimated Useful Life	36 months
Property, equipment and software, at cost	$ 30,412	24,784
Amortization expense	4,400	4,900	$ 4,200
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and software, at cost	$ 11,761	$ 18,336

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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The aggregate amount of recurring noncash expense charged against earnings in the period to allocate the cost of assets over their estimated remaining economic lives.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

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