Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	$ 49,030	$ 50,364
Deposits with clearing organization	26,586	18,034
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	190,963	224,672
Receivables from brokers	36,059	49,458
Securities failed to deliver	10,914	7,799
Clearing organizations	22,957	25,030
Other	2,470	53,954
Total Receivable from brokers, dealers and clearing organizations	263,363	360,913
Receivable from customers	791,631	840,355
Mortgage servicing rights	41,777	41,838
Investments (1)	53,482	53,286
Fair Value Measurement: Liabilities
Drafts payable	37,663	48,011
Bank call loans	148,300	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	143,157	130,658
Payable to brokers	10,232	3,316
Securities failed to receive	24,781	21,513
Other	29,709	9,059
Total payables to brokers, dealers and clearing organizations	207,879	164,546
Payables to customers	521,557	594,833
Securities sold under agreements to repurchase	529,752	651,445
Warehouse payable	11,845	54,341
Senior secured notes	152,195	154,568
Level 1 [Member] | Nonrecurring [Member]
Fair Value Measurement: Assets
Cash	49,030	50,364
Deposits with clearing organization	26,586	18,034
Fair Value Measurement: Liabilities
Drafts payable	37,663	48,011
Level 2 [Member] | Nonrecurring [Member]
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	190,963	224,672
Receivables from brokers	36,059	49,458
Securities failed to deliver	10,914	7,799
Clearing organizations	22,957	25,030
Other	2,470	53,954
Total Receivable from brokers, dealers and clearing organizations	263,363	360,913
Receivable from customers	791,631	840,355
Investments (1)	53,482	53,286
Fair Value Measurement: Liabilities
Bank call loans	148,300	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	143,157	130,658
Payable to brokers	10,232	3,316
Securities failed to receive	24,781	21,513
Other	29,709	9,059
Total payables to brokers, dealers and clearing organizations	207,879	164,546
Payables to customers	521,557	594,833
Securities sold under agreements to repurchase	529,752	651,445
Warehouse payable	11,845	54,341
Senior secured notes	152,195	154,568
Level 3 [Member] | Nonrecurring [Member]
Receivable from brokers, dealers and clearing organizations:
Mortgage servicing rights	41,777	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	49,030	50,364
Deposits with clearing organization	26,586
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	190,963	224,672
Receivables from brokers	36,059	49,458
Securities failed to deliver	10,914	7,799
Clearing organizations	22,957	25,030
Other	2,470	53,954
Total Receivable from brokers, dealers and clearing organizations	263,363	360,913
Receivable from customers	791,631	840,355
Mortgage servicing rights	28,024	28,168
Investments (1)	53,482	53,286
Fair Value Measurement: Liabilities
Drafts payable	37,663	48,011
Bank call loans	148,300	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	143,157	130,658
Payable to brokers	10,232	3,316
Securities failed to receive	24,781	21,513
Other	29,709	9,059
Total payables to brokers, dealers and clearing organizations	207,879	164,546
Payables to customers	521,557	594,833
Securities sold under agreements to repurchase	529,752	651,445
Warehouse Agreement Borrowings	11,845	54,300
Warehouse payable		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	49,030	50,364
Deposits with clearing organization	26,586
Receivable from brokers, dealers and clearing organizations:
Securities borrowed	190,963	224,672
Receivables from brokers	36,059	49,458
Securities failed to deliver	10,914	7,799
Clearing organizations	22,957	25,030
Other	2,470	53,954
Total Receivable from brokers, dealers and clearing organizations	263,363	360,913
Receivable from customers	791,631	840,355
Mortgage servicing rights	41,777	41,838
Investments (1)	53,482	53,286
Fair Value Measurement: Liabilities
Drafts payable	37,663	48,011
Bank call loans	148,300	100,200
Payables to brokers, dealers and clearing organizations:
Securities loaned	143,157	130,658
Payable to brokers	10,232	3,316
Securities failed to receive	24,781	21,513
Other	29,709	9,059
Total payables to brokers, dealers and clearing organizations	207,879	164,546
Payables to customers	521,557	594,833
Securities sold under agreements to repurchase	529,752	651,445
Warehouse payable	11,845	54,341
Senior secured notes	$ 152,195	$ 154,568