Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	$ 85,381	$ 50,364
Deposits with clearing organization	19,935	18,034
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	216,419	224,672
Receivables from brokers	42,763	49,458
Securities failed to deliver	17,541	7,799
Clearing organizations	24,669	25,030
Other	13,916	58,832
Total Receivable from brokers, dealers and clearing organizations	315,308	365,791
Receivable from customers	780,670	840,355
Mortgage servicing rights (1)	6,170	41,838
Investments (2)	53,941	53,286
Fair Value Measurement: Liabilities
Drafts payable	26,759	48,011
Bank call loans	151,900	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	125,548	130,658
Payable to brokers	1,068	3,316
Securities failed to receive	23,491	21,513
Other	22,255	9,059
Total payables to brokers, dealers and clearing organizations	172,362	164,546
Payables to customers	596,441	594,833
Securities sold under agreements to repurchase	432,912	651,445
Warehouse payable (1)	1,486	54,341
Senior secured notes	152,345	154,568
Level 1 [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	85,381	50,364
Deposits with clearing organization	19,935	18,034
Fair Value Measurement: Liabilities
Drafts payable	26,759	48,011
Level 2 [Member] | Nonrecurring [Member]
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	216,419	224,672
Receivables from brokers	42,763	49,458
Securities failed to deliver	17,541	7,799
Clearing organizations	24,669	25,030
Other	13,916	58,832
Total Receivable from brokers, dealers and clearing organizations	315,308	365,791
Receivable from customers	780,670	840,355
Investments (2)	53,941	53,286
Fair Value Measurement: Liabilities
Bank call loans	151,900	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	125,548	130,658
Payable to brokers	1,068	3,316
Securities failed to receive	23,491	21,513
Other	22,255	9,059
Total payables to brokers, dealers and clearing organizations	172,362	164,546
Payables to customers	596,441	594,833
Securities sold under agreements to repurchase	432,912	651,445
Warehouse payable (1)	1,486	54,341
Senior secured notes	152,345	154,568
Level 3 [Member] | Nonrecurring [Member]
Receivable from brokers, dealers and clearing organizations:
Mortgage servicing rights (1)	6,170	41,838
Carrying Value [Member]
Fair Value Measurement: Assets
Deposits with clearing organization		18,034
Carrying Value [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	85,381	50,364
Deposits with clearing organization	19,935
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	216,419	224,672
Receivables from brokers	42,763	49,458
Securities failed to deliver	17,541	7,799
Clearing organizations	24,669	25,030
Other	13,916	58,832
Total Receivable from brokers, dealers and clearing organizations	315,308	365,791
Receivable from customers	780,670	840,355
Mortgage servicing rights (1)	1,993	28,168
Investments (2)	53,941	53,286
Fair Value Measurement: Liabilities
Drafts payable	26,759	48,011
Bank call loans	151,900	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	125,548	130,658
Payable to brokers	1,068	3,316
Securities failed to receive	23,491	21,513
Other	22,255	9,059
Total payables to brokers, dealers and clearing organizations	172,362	164,546
Payables to customers	596,441	594,833
Securities sold under agreements to repurchase	432,912	651,445
Warehouse Agreement Borrowings	1,486	54,300
Warehouse payable (1)		54,341
Senior secured notes	150,000	150,000
Fair Value [Member]
Fair Value Measurement: Assets
Deposits with clearing organization		18,034
Fair Value [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	85,381	50,364
Deposits with clearing organization	19,935
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	216,419	224,672
Receivables from brokers	42,763	49,458
Securities failed to deliver	17,541	7,799
Clearing organizations	24,669	25,030
Other	13,916	58,832
Total Receivable from brokers, dealers and clearing organizations	315,308	365,791
Receivable from customers	780,670	840,355
Mortgage servicing rights (1)	6,170	41,838
Investments (2)	53,941	53,286
Fair Value Measurement: Liabilities
Drafts payable	26,759	48,011
Bank call loans	151,900	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	125,548	130,658
Payable to brokers	1,068	3,316
Securities failed to receive	23,491	21,513
Other	22,255	9,059
Total payables to brokers, dealers and clearing organizations	172,362	164,546
Payables to customers	596,441	594,833
Securities sold under agreements to repurchase	432,912	651,445
Warehouse payable (1)	1,486	54,341
Senior secured notes	$ 152,345	$ 154,568