Revenue Recognition Contract Balances (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Receivables from Customers	$ 83,214	$ 74,962
Contract with Customer, Asset, Net, Noncurrent	2,614	1,270
Contract with Customer, Liability, Current	480	$ 407
Increase (Decrease) in Receivables	8,252
Increase (Decrease) in Other Noncurrent Assets	1,344
Increase (Decrease) in Other Current Liabilities	73
Contract with Customer, Liability, Revenue Recognized	$ 697

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time, classified as noncurrent.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

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Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

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Amount of increase (decrease) in current liabilities classified as other.

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Amount of increase (decrease) in noncurrent assets classified as other.

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The increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.

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Amount due from customers for fees and charges arising from transactions related to the entity's brokerage activities and operations.

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