Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value on Recurring Basis (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015
Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	$ 51,147,000	$ 50,364,000
Deposits with clearing organization	11,625,000	18,034,000
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	155,726,000	224,672,000
Receivables from brokers	27,691,000	49,458,000
Securities failed to deliver	16,782,000	7,799,000
Clearing organizations	16,399,000	25,030,000
Other	39,221,000	58,832,000
Total Receivable from brokers, dealers and clearing organizations	255,819,000	365,791,000
Receivable from customers	798,048,000	840,355,000
Mortgage servicing rights (1)	273,000	41,838,000
Investments (2)	56,041,000	53,286,000
Fair Value Measurement: Liabilities
Drafts payable	31,414,000	48,011,000
Bank call loans	132,000,000	100,200,000
Payables to brokers, dealers and clearing organizations:
Securities loaned	133,205,000	130,658,000
Payable to brokers	6,626,000	3,316,000
Securities failed to receive	13,862,000	21,513,000
Other	475,000	9,059,000
Total payables to brokers, dealers and clearing organizations	154,168,000	164,546,000
Payables to customers	517,681,000	594,833,000
Securities sold under agreements to repurchase	528,113,000	651,445,000
Warehouse payable (1)		54,341,000
Senior secured notes	152,720,000	154,568,000
Level 1 [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	51,147,000	50,364,000
Deposits with clearing organization	11,625,000	18,034,000
Fair Value Measurement: Liabilities
Drafts payable	31,414,000	48,011,000
Level 2 [Member] | Nonrecurring [Member]
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	155,726,000	224,672,000
Receivables from brokers	27,691,000	49,458,000
Securities failed to deliver	16,782,000	7,799,000
Clearing organizations	16,399,000	25,030,000
Other	39,221,000	58,832,000
Total Receivable from brokers, dealers and clearing organizations	255,819,000	365,791,000
Receivable from customers	798,048,000	840,355,000
Investments (2)	56,041,000	53,286,000
Fair Value Measurement: Liabilities
Bank call loans	132,000,000	100,200,000
Payables to brokers, dealers and clearing organizations:
Securities loaned	133,205,000	130,658,000
Payable to brokers	6,626,000	3,316,000
Securities failed to receive	13,862,000	21,513,000
Other	475,000	9,059,000
Total payables to brokers, dealers and clearing organizations	154,168,000	164,546,000
Payables to customers	517,681,000	594,833,000
Securities sold under agreements to repurchase	528,113,000	651,445,000
Warehouse payable (1)		54,341,000
Senior secured notes	152,720,000	154,568,000
Level 3 [Member] | Nonrecurring [Member]
Receivable from brokers, dealers and clearing organizations:
Mortgage servicing rights (1)	273,000	41,838,000
Carrying Value [Member]
Fair Value Measurement: Assets
Deposits with clearing organization		18,034,000
Carrying Value [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	51,147,000	50,364,000
Deposits with clearing organization	11,625,000
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	155,726,000	224,672,000
Receivables from brokers	27,691,000	49,458,000
Securities failed to deliver	16,782,000	7,799,000
Clearing organizations	16,399,000	25,030,000
Other	39,221,000	58,832,000
Total Receivable from brokers, dealers and clearing organizations	255,819,000	365,791,000
Receivable from customers	798,048,000	840,355,000
Mortgage servicing rights (1)	268,000	28,168,000
Investments (2)	56,041,000	53,286,000
Fair Value Measurement: Liabilities
Drafts payable	31,414,000	48,011,000
Bank call loans	132,000,000	100,200,000
Payables to brokers, dealers and clearing organizations:
Securities loaned	133,205,000	130,658,000
Payable to brokers	6,626,000	3,316,000
Securities failed to receive	13,862,000	21,513,000
Other	475,000	9,059,000
Total payables to brokers, dealers and clearing organizations	154,168,000	164,546,000
Payables to customers	517,681,000	594,833,000
Securities sold under agreements to repurchase	528,113,000	651,445,000
Warehouse Agreement Borrowings	0	54,300,000
Warehouse payable (1)		54,341,000
Senior secured notes	150,000,000	150,000,000
Fair Value [Member]
Fair Value Measurement: Assets
Deposits with clearing organization		18,034,000
Fair Value [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	51,147,000	50,364,000
Deposits with clearing organization	11,625,000
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	155,726,000	224,672,000
Receivables from brokers	27,691,000	49,458,000
Securities failed to deliver	16,782,000	7,799,000
Clearing organizations	16,399,000	25,030,000
Other	39,221,000	58,832,000
Total Receivable from brokers, dealers and clearing organizations	255,819,000	365,791,000
Receivable from customers	798,048,000	840,355,000
Mortgage servicing rights (1)	273,000	41,838,000
Investments (2)	56,041,000	53,286,000
Fair Value Measurement: Liabilities
Drafts payable	31,414,000	48,011,000
Bank call loans	132,000,000	100,200,000
Payables to brokers, dealers and clearing organizations:
Securities loaned	133,205,000	130,658,000
Payable to brokers	6,626,000	3,316,000
Securities failed to receive	13,862,000	21,513,000
Other	475,000	9,059,000
Total payables to brokers, dealers and clearing organizations	154,168,000	164,546,000
Payables to customers	517,681,000	594,833,000
Securities sold under agreements to repurchase	528,113,000	651,445,000
Warehouse payable (1)		54,341,000
Senior secured notes	$ 152,720,000	$ 154,568,000