Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Assets and Liabilities (Schedule of Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis) (Details)

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Fair Value of Assets and Liabilities (Schedule of Fair Value of Assets and Liabilities Measured on a Nonrecurring Basis) (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Liabilities    
Contingent consideration payable $ 1,756 $ 2,104
Carrying Value | Fair Value, Measurements, Nonrecurring    
Assets    
Cash and cash equivalents 145,417 172,103
Notes receivable, net 6,522 47,369
Other receivables, net 122,154 60,707
Total assets 332,198 330,953
Liabilities    
Accrued compensation 18,828 33,343
Commissions and fees payable 95,937 67,221
Accounts payable and accrued liabilities 50,449 38,374
Accrued interest 261 232
Notes payable, net 98,997 96,849
Total liabilities 264,472 236,019
Fair Value | Level 2    
Liabilities    
Notes payable, net 100,732 99,129
Fair Value | Fair Value, Measurements, Nonrecurring    
Assets    
Cash and cash equivalents 145,417 172,103
Notes receivable, net 6,522 47,369
Other receivables, net 122,154 60,707
Total assets 332,198 330,953
Liabilities    
Accrued compensation 18,828 33,343
Commissions and fees payable 95,937 67,221
Accounts payable and accrued liabilities 50,449 38,374
Accrued interest 261 232
Notes payable, net 100,732 99,129
Total liabilities 266,207 238,299
Fair Value | Fair Value, Measurements, Nonrecurring | Level 1    
Assets    
Cash and cash equivalents 145,417 172,103
Notes receivable, net 0 0
Other receivables, net 0 0
Total assets 145,417 172,103
Liabilities    
Accrued compensation 0 0
Commissions and fees payable 0 0
Accounts payable and accrued liabilities 0 0
Accrued interest 0 0
Notes payable, net 0 0
Total liabilities 0 0
Fair Value | Fair Value, Measurements, Nonrecurring | Level 2    
Assets    
Cash and cash equivalents 0 0
Notes receivable, net 6,522 47,369
Other receivables, net 122,154 60,707
Total assets 186,781 158,850
Liabilities    
Accrued compensation 18,828 33,343
Commissions and fees payable 95,937 67,221
Accounts payable and accrued liabilities 50,449 38,374
Accrued interest 261 232
Notes payable, net 100,732 99,129
Total liabilities 266,207 238,299
Receivables from clearing brokers | Carrying Value | Fair Value, Measurements, Nonrecurring    
Assets    
Receivables 55,842 48,543
Receivables from clearing brokers | Fair Value | Fair Value, Measurements, Nonrecurring    
Assets    
Receivables 55,842 48,543
Receivables from clearing brokers | Fair Value | Fair Value, Measurements, Nonrecurring | Level 1    
Assets    
Receivables 0 0
Receivables from clearing brokers | Fair Value | Fair Value, Measurements, Nonrecurring | Level 2    
Assets    
Receivables 55,842 48,543
Receivables from other broker-dealers | Carrying Value | Fair Value, Measurements, Nonrecurring    
Assets    
Receivables 2,263 2,822
Receivables from other broker-dealers | Fair Value | Fair Value, Measurements, Nonrecurring    
Assets    
Receivables 2,263 2,822
Receivables from other broker-dealers | Fair Value | Fair Value, Measurements, Nonrecurring | Level 1    
Assets    
Receivables 0 0
Receivables from other broker-dealers | Fair Value | Fair Value, Measurements, Nonrecurring | Level 2    
Assets    
Receivables $ 2,263 $ 2,822